EMERY WHEELS FOR GUMMING SAWS.

In the illustration herewith, the operation of gumming saws with an emery wheel is vividly represented, the frame affording sufficient support for the side of the saw where the teeth are being ground, and the arrangement being a simple one, readily made at any work bench or machine where a shaft is run upon which an emery wheel can be placed. The operation itself involves only the simplest mechanical knowledge and but a rudimentary experience in the handling of tools, yet the desirability of this method of sharpening saws is largely dependent upon the kind of emery wheel used and the rate of speed at which it is run.

EMERY VULCANITE SAW GUMMER.

The vulcanite emery wheels made by the New York Belting and Packing Company have especial advantages for this kind of work. They are strong and safe at the highest speed at which it is desirable to run them, the company recommending that they never be run at a less rate than 6,000 feet per minute circumferential speed, and from that up to 8,000 and 10,000 feet per minute, although the lowest named speed is rather above the ordinary limit of many other kinds of emery wheels, and attempts to run other wheels at or beyond this limit have frequently resulted in serious accidents, from the breaking of the wheels. The higher rate of speed, which not only cuts faster, but, in the case of the vulcanite emery wheel, prolongs the life of the wheel, is concededly safe with the vulcanite wheel. Thus run, it is not likely to wear out of true, the operator does not have to bear on so hard, and the wheel retains its shape much better than when run at a slow speed. The nature of the wear of the working surface in the vulcanite wheel is claimed to be essentially different from that in wheels where the emery is fixed in its place by other methods, the rubber affording an elastic foundation or cushion, from which the particles of emery slightly protrude. This not only insures more efficient work from the cutting edges of the emery, as they become changed by use, but allows of more access of air to the work, thus tending to prevent casehardening of the edges of the metal being ground.

In addition to wheels with bevel shaped grinding surfaces, as represented in the engraving, the company also make wheels with round grinding surfaces, and this kind is always considered best for large saws.

In technical terms this is a living species of cladodont shark, named by Mr. GarmanChlamydoselachus anguineus.

The specimen here figured was found in a miscellaneous collection of fishes, etc., in alcohol, furnished the Museum of Comparative Zoology by Professor H. A. Ward, who purchased them in Japan. It was soon recognized as not only belonging to a new family, but one closely allied to certain forms supposed to have become extinct in the Carboniferous time. This discovery displacesCeratodusfrom the position of the oldest living type of the vertebrata.

The term Chlamydoselachus is applied on account of the curious frill-like mantle that surmounts the first gill cover. The term is made up of two Greek words implying mantle and shark. Six gill openings, and certain structure of the brain, remove this form from the present known sharks. Its affinity to some of the earliest known sharks, those of the middle Devonian, render it of great interest and importance to science. The family characters which this form represents, under the termChlamydoselachidæ, are: Body elongate, with a depressed head. The eyes are lateral, with no nictitating membrane. The nasal cavity is separate from that of the mouth. The mouth is situated anteriorly, like that of some fishes. The teeth have broad, backward extended bases and slender cusps. The spiracles are present. One dorsal fin, spineless, is present. There is also an anal fin, and a caudal with no pit at its root. The first gill cover is free across the isthmus. The intestine has a spiral valve.

The generic characters are: Six gill openings, opercular flap, first gill cover, broad. Teeth similar in both jaws; each with three slender, curved, subconical cusps, separated by a pair of rudimentary denticles or a broad base. There is no median upper series of teeth in front, but there is a series below, on the symphysis. The mouth is wide, and has no labial folds at the angles. The pupil is horizontally elongate; the fins are broad, the caudal without a notch.

The total length of this shark is nearly five feet. Its greatest width, across the ventrals, is seven inches. Its resemblance to a snake is very striking. Its elongated body, long, flattened head, anterior mouth, and sinister expression of the eyes are quite suggestive of the ophidians. There are fifty-one rows of teeth, and six teeth in each row; the whole number at one time in function is 306. The brain is very small.

The present state of icthyological science recognizes eliminations that have been made from its main body. Comprehensively, a fish is a cold-blooded vertebrate, adapted for life in the water, breathing by means of gills, having the limbs, if present, in the form of fins, the smaller members being represented by cartilaginous rays connected by membrane. One or more fins are developed on the median line of the body.

The lancelets, myzonts, myxinoids, hag fishes, lampreys, sharks, and rays are recognized as differing sufficiently from the true fishes to entitle them to places of class distinction.

THE FRILLED SHARK—THE OLDEST LIVING TYPE OF VERTEBRATES.

The true fishes form one class; the elasmobranchs, sharks, and rays, another class; the marsipobranchs, myxinoid fishes, hag fishes, and lampreys, a class; and the lancelets and cirrostomes, a class. It will be seen, then, that technically there are four classes of fish-like vertebrates, where but one—fishes—has heretofore been recognized. The lancelets, as is well known, are the lowest in the scale, their structure being extremely simple. The skull in this class is undeveloped, the brain not distinctly differentiated, nor is there any heart.

The term Leptocardii, which designates this class, means thin heart, in reference to the simplicity of this portion of the arterial system.

At first sight of the mouth of the frilled shark, which is figured here, the teeth have a singular and wholly unnatural appearance, appearing like indented, leaf-like organs; but it is seen that there are three fangs, serpent-like, on a base, and several rows of them give the peculiar appearance, arranged as they are consecutively from before inward.

The Port Jackson sharks, of the familyHeterodontidæ, have long been regarded as of great interest to paleontologists, from their being closely related to some extinct sharks. Under the term Cestracion (nowGyropleurodus), these sharks are known to naturalists. A species,G. francisci, is now found off the coast of California.

Cestracion phillipiis found in the Australian seas. The term cestracion is from the Greekkestra, a weapon. Many of the extinct species are known by the preservation of this spine, which being of more durable structure is preserved after all other traces of the creature have passed away.

TICHENOR & WALKER'S IMPROVED STUMP PULLER.[FOR DESCRIPTION SEE PAGE 132.]

The mouth of the frilled shark, as seen in our engraving, is peculiar appearing for a shark, as this important part is usually situated far beneath. In this respect, the anterior aspect of the mouth, there is resemblance to that of the great rhinodon, the largest living fish, measuring 70 feet in length. The general appearance of this shark is, however, extremely different from that of the frilled shark. The rhinodon is immensely bulky, the head being quite as deep and wide as any other portion. A very interesting structure, and one little known, belonging to the latter is a set of whalebone-like fringes along the gills, arranged comb-like. These frills have much the same functions of those in the whalebone or right whales. The food of the creature is mostly of sea jellies and other soft pelagic animals, which are strained into the throat by means of this adaptation. The great basking shark has this structure. This shark has been taken off Block Island measuring, according to authority, nearly seventy feet. It is theCetorhinus, or bone shark, also so called. Large as these creatures are, they are harmless, most fortunately, their teeth being very small. Their food being of gelatinous animal matter, the masticating apparatus is not required to be of any considerable size or strength. The more harmful sharks are of moderate dimensions, in which the teeth are very large. In the largest species of "maneater" shark living, the teeth are about two inches in length. Some of the great carcharodon-like fossil sharks have teeth measuring five inches and a half in length. One in my possession has that measurement. Judging from the size of the shark, which has a tooth two inches in length, the extinct species here indicated must have been much over one hundred feet in length. Such enormous size can more readily be accommodated in the vast ocean than that of the great land beasts on their appropriate element. I am indebted to papers on this subject by Mr. Garman, of Cambridge, Mass., for material of this account.

J. B. H.

Immediatelyafter eating, a person weighs more than before it.

The bench is composed of side pieces, legs, end pieces, and a central cross brace. At one end it is provided with stationary top pieces having curved inner edges, as shown in the upper view, which are covered with a thin strip of angle iron extending up flush with the top and bent to conform with the curved edge. To the upper ends of the legs are hinged supports adapted to extend upward to form continuations of the legs, to engage with and hold an ironing board in a horizontal position. A tongue formed upon the free end of each support enters a socket box fitted in a recess formed in the board, so that the hinged lids of the boxes are flush with the bench surface of the board. When the board is in position to be ironed upon, the hinged lids rest against the sides of the supports, an opening in the lids receiving pins projecting from the sides of the supports. The lids are held in this position by suitably arranged buttons. By this means the ironing board is securely fixed in its elevated position. The rigidity of each support is promoted by another button attached to its inner side, and which enters a slot in the top edge of the side piece. To convert the ironing board into a bench, the board is lifted up and the supports closed down within the bench, as shown in the lower view. The wraps used upon the board are then placed neatly over the supports. The board itself is then turned over and its narrow end slid under the projection of the angle iron to a bearing upon the upper edges of the bench frame. The board now forms a smooth top for the bench. The under side of the ironing board, when forming a seat, is recessed near each side of its square end. Each recess is covered by a metal plate having a diamond-shaped opening to receive the elongated head of a bolt secured to the inner face of the bench side pieces. The square end of the board is thus held to the bench, the narrow end being held by the angle irons.

WELLER'S COMBINED BENCH AND IRONING BOARD.

This invention has been patented by Mr. Daniel H. Weller, of Boyertown, Pa.

GULICK'S IMPROVED BLIND STOP.

By means of the simple attachment here shown, the blind may be securely held in any desired position. Secured to the lower cross bar is a metal plate, bent at right angles to form flanges, the projecting one of which is finely corrugated. The plate is held to the bar by screws passing through the other flange. Across the face of the outer flange is secured a spring retaining strip, which bears against the corrugated face and which carries a set screw. To the end of the slat bar is secured a corrugated strip, which is passed between the flange and its strip, the corrugated faces resting against each other, as shown in the right hand view.

This device will hold the slats in any required position, but when the slat bar is subjected to a positive pull, the strip will slip upon the face of the flange, against which it will be held by the action of the spring strip. By means of the set screw, the parts may be so locked together as to prevent the turning of the slats from the outside.

This invention has been patented by Mrs. Lizzie T. Gulick, of Corsicana, Texas.

Some mistake appears to have been made in the recent announcement that the British Government are sending out a number of eighty ton guns for the coast defense of Esquimault and Victoria. Twelve sixty-four pounders have been sent out from England, not for the armaments of the forts, but to be placed on board the British ships of war belonging to the Pacific squadron or to go into the naval reserves. Some time ago the British Minister of War made application to the Canadian Pacific Railway to know if they could transport one or more eighty ton guns over their road. An estimate of the cost was given, with the model of a car composed of three trucks, which it was proposed to use if the shipment was made. Since then nothing has been heard of the eighty ton guns. The officer in command of the British Columbia district does not speak very creditably of the condition of the armament at that point. The artillery armament is described as old, the carriages and limbers are reported rotten and are falling to pieces, while the guns are without sights. The batteries at Victoria and Esquimault, the officers say, are in a discreditable condition.—N. Y. Evening Post.

LA FOLLETTE'S BOOT CRIMPER.

The crimper herewith illustrated has a yoke-shaped stationary portion, the jaws of which are formed with transverse corrugations. The top of this yoke has a longitudinal slot, in which are pivoted the upper reduced ends of movable inner jaws, whose operative faces have transverse corrugations, arranged to always meet and fit within the corresponding corrugations of the outer jaws. These inner jaws are normally held open by a spring. The operating or crimping screw slides freely through the slot in the yoke, extending between the inner jaws, and on its lower portion fits a wedge-shaped clamping block, which is drawn up between the inner jaws by turning the operating screw. The outer end of this screw being placed in an aperture in the heel of the last, or in other suitable position relative to a form over which the leather is to be crimped, and the edges of the leather placed between the jaws, the leather may be strained about its forming block as desired by simply rotating the screw.

This invention has been patented by Mr. Elery B. La Follette, of Flemington, West Va.

The object of this invention, which has been patented by Mr. Geo. W. Jaques, of Burton, O., is to provide a plasterer's hawk in which the board on which the mortar is received, and which is subjected to expansion and contraction due to alternate moistening and drying, may be rendered light and rigid and, at the same time, be free to expand and contract without warping or cracking. In the center of the board is secured a bolt, upon which is received a handle having a nut in its outer end fitting the end of the bolt. A circular concave plate is placed on the bolt, between the handle and board, with its concave side toward the board. Between the plate and board is held an elastic rubber washer, which is compressed by screwing the handle down.

The plate has a plane edge, which is secured to the board by screws, and in the edge are four notches for receiving the ends of wire frames that extend a short distance under the plate, by which they are clamped to the board. Each frame consists of a wire, bent to the shape shown in the upper view in the engraving. Through the end loops are passed screws, projecting from the board, and the center of each frame is secured to the board by a clip, the clips and bolt being arranged in a line parallel with the grain of the wood. The frames support the edges of the board, and the loops permit of the lateral movement of their screws and the portions of the board by which they are carried. This hawk weighs, even when thoroughly soaked, only one pound and a half, the old style weighing from three to five pounds.

JAQUES' PLASTERER'S HAWK.

By means of this device wood may be measured by the cord or fractional parts of a cord, as occasion may require. The sill frame consists of two longitudinally ranging timbers connected by cross bars. Near one end of the timbers are fixed uprights, braced to each other and to the timbers. To the inner faces of the sills are screwed a series of headed pins, the first one being exactly one foot from the inner face of the end posts, and the others being spaced one foot apart. Two posts, braced together by rods, are adapted to stand on the sills, and to the inside face of each post is attached, by coach screws, a metal plate provided with a hook at its lower end, adapted to engage with the shank of one of the headed screw pins of the sills. Attached to each post is a brace with two arms, and formed at its lower end with a notch to engage the pins on the sills. The metal plates and braces are slotted for the passage of the screws, so that the movable frame may be quickly and easily set perfectly plumb, whichever opposite pair of the sill pins may be engaged by the hooked plates. The posts are exactly four feet high, and one is marked by cross lines one foot apart. It is apparent that, to measure a cord, the frame is moved to the eighth set of pins and the wood is piled to the tops of the posts. To measure half a cord, the hooks are engaged with the fourth pins. By adjusting the hooks to the first pair of pins, and filling the wood in between the end posts up to the first cross line on the post, a single foot of wood can be measured, or up to the second line for two feet, and so on. Thus a cord or any fractional part can be readily measured. To disengage the frame, it is only necessary to tilt it forward toward the fixed posts, when it may be shifted to any point along the sill frame.

BROUGHTON'S ADJUSTABLE WOOD MEASURING RACK.

This invention has been patented by Mr. Horace L. Broughton, whose address is P. O. box 320, Marblehead, Mass.

At last a mechanical combination and device has been produced, and a man's labor and study crowned with success, in the production, for the convenience of engineers, of a simple and compact device known as the Penberthy injector or boiler feeder.

Its mechanical construction is very simple, but perfect. All its parts are movable and convenient of access (not being screwed in), its working so complete that an inexperienced person can operate it with success and perfectness. Its adaptability to all classes of boilers, such as stationary, portable, traction, marine, and locomotive, and its working on each, makes it very desirable, and recommends it to all classes of engineers. The automatic working of this injector is of very great advantage, as by this mechanical construction it works under all conditions of shakes, jars, and concussions. In case of a break, or the suction is to be removed and then returned, it picks up or begins working without any aid, assistance, or attention from the engineer, thereby relieving of much care and annoyance. Its convenience of access is of very great consideration and importance, owing to the advantage of cleaning and examining its interior parts.

The working parts of this injector are stationary in their work, thereby causing comparatively no wear in its mechanical parts. The inventor seems to have combined common sense with mechanical science, by leaving out all complications, and combining in the injector every convenience of operating, getting at, and putting it on the boiler.

The body is of a single cylinder or barrel, with two jets inside, "steam and combining," and governed by an automatic swinging overflow. The injector is operated by the opening or closing of the globe valves. It is connected to the boiler and pipes with uniform and interchangeable square centered unions, and can be put on or taken off very quickly without any annoyance or injury, and the only tool required being an ordinary wrench.

Another great point gained in this injector is its great range of working capacity. It will lift water twenty-five feet perpendicular, or take it a hydraulic pressure and force it into the boiler at a temperature of from 140° to 180° Fah. It will work under a steam pressure of from 20 to 140 lb. It will also lift and force water at a very warm temperature (say 120° Fah.) in tank or well, and under all circumstances and at all points it works automatically. The inventor and manufacturers of the Penberthy injector have great confidence in its working qualities, and to satisfy engineers of its merits and perfectness of work, solicit a trial. From observation, a brilliant future is in store for this little wonder of simplicity and compactness, which is a model of mechanism in appearance and finish.

PENBERTHY INJECTOR.

For prices, etc., address Jenkins Bros., 71 John St., New York, 13 So. 4th St. Philadelphia, and 105 Milk St., Boston, agents for this injector.

This simple and readily adjustable protector may be quickly applied to and removed from a hat or bonnet, without injuring its delicate trimmings, and may be adjusted to fit large or small hats. The main portion of the protector, which alone will be used to cover hats of small or medium size, consists of a piece of some light waterproof fabric strengthened about the margin with an inside facing. At the inner face of the body are secured a couple of narrow strips of suitable fabric (Fig. 2), forming casings for drawing strings. At the opposite edges of the facing are attached small rings, through either series of which a drawing string may be passed.

The extension piece (Fig. 1) of the protector consists of an endless band of waterproof fabric, like that of the body, provided at its edges with bindings, to which rings for drawing strings are secured. The protector can readily be adjusted and held upon a small or medium sized hat by properly manipulating the drawing strings. To adapt the protector to a large hat, the extension piece is united to the main piece by a string passed through the inner series of rings on the facing and through one of the series of rings on the extension piece. A string is then passed through the other rings of the extension piece, when the protector can be held to the hat by adjusting the drawing strings. It is evident that this protector may be applied over a hat without danger of crushing the most delicate trimmings.

HOPKIRK'S PROTECTOR FOR LADIES' HATS.

This invention has been patented by Mrs. W. H. Hopkirk, of Agency, Iowa.

The stump puller shown in the accompanying engraving (page 130) is exceedingly powerful, as, by a system of compound levers, a pull of one pound on the operating bar will exert a pull of 384 pounds on the stump, and if the lifting chain be passed around a single pulley, this power is doubled. With one of these machines one man has pulled a green maple stump two feet in diameter from clay soil. The pulling mechanism is supported by a tripod, to the upper end of which is secured a chain carrying a bar or plate provided with a bearing in which slides a notched bar. Meshing with the notches of this bar are the teeth of a pawl, which is so connected, by levers, with the operating handle that the downward movement of the latter will raise the pawl and notched bar and the chain attached to its lower end. A sliding bolt then holds the notched bar in its raised position, when the handle can be raised to enable the pawl to engage with the next lower teeth of the bar. Thus, by a succession of up and down movements of the handle, the notched bar may be elevated its entire length, or until the stump is pulled completely out. It will be seen that the sliding bolt permits of the upward, but prevents the downward, movement of the notched bar when the pawl is disengaged and slides downward. But, by means of a suitably arranged hand lever, the pawl may be moved so as to be out of contact with the bar, and, at the same time, the bolt, which is pressed forward by a spring, may be moved to disengage it from the notch in the bar, which may then be adjusted in any desired position. The machine is built of steel and malleable iron.

This invention has been patented by Messrs. R. R. Tichenor and P. Walker, of Henning, Minn.

The idea seems to prevail that the United States is absolutely helpless against a naval attack from England. I think this idea is entirely erroneous. There is the pneumatic gun, capable now of throwing 300 lb. of nitro-glycerine, which amount could easily be increased to 1,000 lb. For the value of one modern ironclad, 150 steamers with such a gun could be put in service in two weeks by the United States, because any steamer of 100 feet or over would answer; while the gun, being a mere tube, subjected to but 1,000 lb. of air per square inch, with air-compressing machinery, is all so available and quickly built that a month would put the United States into possession of 500 of them. If, now, 20 such steamers be told off for each ironclad sent against us, even if two-thirds were sunk, they would, before being entirely demolished, succeed in depositing 5 to 10 tons of nitro-glycerine on the deck of the ironclad, and exploding it.

Would not the effect of repeated explosions of 1,000 lb. of nitro-glycerine blow the deck in, dismount the guns and engine, and shake the armor loose, as the explosions of the Monitors' guns did when they were in service in the late war—the heads of bolts and other fastenings of the armor flying off from the concussion.

Then there is the submarine boat, that has already stayed under water thirty minutes with its crew, and been easily and correctly guided. What is in the way of using ten such boats to each ironclad, one of which would unquestionably succeed in placing 1,000 lb. of nitro-glycerine under the ironclad, the explosion of which would be heard from? Because the explosion of 90 lb. of gun-cotton did not materially damage an ironclad, can it be reasoned that 1,000 lb. of nitro-glycerine, which would have twenty-five times the force of 90 lb. of gun-cotton, would be equally ineffective? Hardly, I think.

Nets, etc., would not prevent such boats from diving under them, while they would only impede the speed and maneuvering of the ironclad, and render her more easily approached.

Blucher, the German cavalry officer, insisted that it was the impression and belief existing in Germany that Napoleon was invincible, and the Germans helpless, that alone prevented them from conquering. When the occasion came when he could demonstrate this, the Germans and allies easily defeated and dethroned Napoleon.

It is similarly true in this country, for too many believe that the English ironclad is invincible, and this impression makes cowards of too many. Give the nitro-glycerine gun and submarine boat a trial, if occasion arises, and England's ironclads will succumb as easily as Napoleon when sufficient power of the right kind was brought to bear on him. The right kind of power to apply to England is nitro-glycerine and dynamite, which could be ready with guns and boats in a month or less. One hundred days sufficed to build the first Monitor many years ago, and much less time will be needed for dynamite guns.

Wayne.

Platinum has not been much used in electroplating, notwithstanding its hard, durable, and protective properties. This is, perhaps, chiefly owing to the practical difficulty of obtaining a good firm "reguline" deposit. A process for effecting this has, however, been brought out recently by a Mr. Bright, whose patents have been acquired by the Bright Platinum Plating Company, and are in actual operation in London at works established there. Platinum has the advantage of keeping its color where silver, brass, or copper becomes discolored, and will, to some extent at least, replace the use of these metals in electrotyping. It will be highly useful in plating chemists' crucibles and so on. German silver, for example, plated with platinum can be used to manipulate strong acids. By the Bright process, platinum can be deposited on any surface which can be electroplated with other metals.

The invention herewith illustrated relates to a device for cleaning brushes and combs. It consists of a handle or body of suitable form, provided at one end with a brush, and at the opposite end with thin curved fingers of metal, or equivalent elastic material, adapted to enter between the teeth of the comb or the bristles of the brush. In making use of the device the hooks are employed to loosen and remove, as far as possible, the hairs or other foreign matter, after which the brush is employed to complete the operation. It is intended to afford a cheap, simple, and efficient means of cleaning articles in daily use in every household, and is virtually sure, considering the low cost at which it can be manufactured, to become a staple article of merchandise. The invention has been patented by Mr. J. O. Brookbank, of Driftwood, Cameron County, Pa., to whom all particulars relating to purchase of rights for the United States and Canada should be addressed.

BROOKBANK'S COMBINED BRUSH AND COMB CLEANER.

To the Editor of the Scientific American:

I would like to call your attention to a reported coincidence, described in a letter in the LondonTimesof December last. An interview with captain and crew of a vessel just then arrived at Sydney, Australia, from Tonga Islands, is given. The captain is represented assaying that while lying off the islands on the night of the 31st of August, 1886, he observed a most terrific eruption of a volcano situated on one of them, accompanied by earthquake shocks, and the vessel received showers of dust and ashes. The occurrence on the same night with the Charleston earthquake on this continent is curious, to say the least. The statement might be acceptable to those of your readers interested in seismic disturbances.

P. Max. Foshay.

Beaver Falls, Pa., February 2, 1887.

To the Editor of the Scientific American:

I write to relate an incident which may be of interest to some of the readers of your valuable paper. There is a bar iron mill, situated in a neighboring town four miles from here, that has been on fire three or four times, in which the English sparrow might be called the incendiary. These sparrows pick up old pieces of cotton waste, which they build in their nests, among the timbers of the roof of the mill, and in every case of the fires above mentioned, these nests were the cause, either from spontaneous combustion or from sparks from the hot iron striking and lodging in the nest. If you could suggest some way of getting rid of the sparrows, I think the manager of the mill would be glad to adopt your plan.

R. W. Kear.

Pottsville, Pa., February 14, 1887.

To the Editor of the Scientific American:

Perhaps charcoal has not often been observed as occurring naturally with mineral coal, though, as a result of metamorphism, graphite is not uncommon in coal districts.

In a variety of bituminous coal that comes from Tennessee, and that is largely used in this State, there are to be seen along in the cleavage planes films of true charcoal, in varying quantity, but commonly thin. This coal has been coming to us for several years, and all the while I have noticed in it the presence of the charcoal. I have scarcely ever put coal into the fire without making the observation; and there is perhaps not a lump, of size at all considerable, that does not contain these films.

On close examination, I have frequently found that the surface of the films on the broken lumps contains a delicate tracery, closely resembling vegetable impressions. The tracery is not so well marked as a fossil imprint, but not so indistinct as to escape notice.

J. F. B.

Emory College, Ga.

To the Editor of the Scientific American:

In reading of the habits of the wading birds, and particularly of the crane, I do not find that naturalists give any account of their manner of attracting their prey at night. My attention was called to the matter while gigging for fish, by frequently observing dim phosphoric lights appear and disappear along the shore like jack o' lanterns, which I for a long time supposed them to be. Oh one occasion I fired at such a light, and brought down a large blue crane, on which the phosphoric spots were clearly visible after death. There are two such spots; the larger being high up on the breast and the smaller at the bottom of the breast bone, the bird having power to reveal and conceal them at will. I have since stuffed many of the water walkers, and find that all have the same general arrangement of the feathers, and, as I believe, the same power of lighting up the water to attract the fish. Will some naturalist who is posted on this subject please throw some further light upon it, for the benefit of science?

Isaac N. Worrall.

Topeka, Kansas.

A correspondent in British Columbia, who is engaged in the business, gives us the following practical information:

Noticing your reply to a correspondent anent canned goods, I recently opened several cans of salmon that were processed in July of 1879, 1880, 1881, and on comparing them with last season's cans, found it impossible to detect the slightest difference. I hold that if a can is once perfectly sealed, the contents will remain unaltered as long as the metal casing remains intact.

A can will keep if every portion of the contents has been subjected to a temperature of 212° Fah., whether the air is expelled or not, as my experiments have conclusively proved.

When I first began the business, I was taught that the air unless expelled would cause the contents to deteriorate, and that was the reason the cans were vented. I soon found it was a mistake. The venting is done for the purpose of testing for leaks. A tight can has a sound that cannot be mistaken for a leaky one. If your correspondent boils his fish, flesh, or fowl with the vents open, he will have dry cans for his pains. The vents must be closed when cooking, and opened, in the case of meats, after boiling one hour, then closed and returned to kettle, and boil three hours for fish and less for meat without bone. Fruit is vented and closed when finished.

S. H.

It is a popular belief that the woods and fields in winter time are void of bird life, and are what they appear at a distance—a cold, bleak, and desolate waste.

This opinion, however, is not correct. It is true that the birds, which were so numerous during the summer, have left us and gone to their winter homes, but as they departed an entirely different fauna started from a colder climate, and gradually took their place. I refer to the birds of the northern part of Canada and the fur countries, whose summer homes are in these desolate regions, and which on the approach of winter are driven southward, making a temporary stay with us until the rigors of an Arctic winter shall have departed, and once more left their homes in an inhabitable condition.

A glance at these birds will take one into the same localities that have been so often traversed in the summer time, and once within the woods, the fact that they are cold and leafless is lost sight of. One can now find birds entirely different from any that he has heretofore seen, and at the same time learn several facts of interest concerning birds with which he considers himself well acquainted; as, for instance, the American goldfinch, which is supposed to migrate in the fall, will be found in the swampy woods in large flocks, but with plumage so changed that they will probably not be recognized, being of a somber brown color, and sexes undistinguishable. Why hundreds of a species, the majority of which migrate regularly, and which do not reach us until late in the spring, should change their dress and remain with us throughout our most severe winters is a problem.

In company with them will often be found the pine linnet and common red poll. These little finches are rather rare, and are seldom found together in any great numbers. They leave the North in large flocks, but as they journey southward break up into smaller and smaller companies, until only a few are left together. These join interests with the nearest goldfinches, and remain with them throughout the winter.

The results of a visit to the fields, on some clear day, will often repay a somewhat wearisome tramp. The snow buntings and shore larks frequent such places in large numbers, and a locality where the ground has been swept bare of snow, or is covered with a growth of weeds, is a favorite feeding ground.

Their food consists entirely of the seeds, and a spot once chosen by them is seldom forsaken until all in this line has been eaten.

The buntings will be found in flocks of from a dozen to two hundred, and in some even more. Their appearance when flying is pure white, but the upper parts of a specimen in the hand will be found mostly black. They are extremely shy, and when approached spring into the air and dart away in a manner that would indicate their intention of departing for the next county; but should you return that way in the course of half an hour, you will, in all probability, find them in the same place.

The shore larks, although feeding on the same grounds, seldom mix with the buntings, preferring to keep in flocks by themselves, and are worthy of attention, inasmuch as they have one marked peculiarity; this is the small tuft of feathers on each side of the head, resembling minute horns, which are raised and lowered at pleasure. (See cut.)

The majority of these birds reach us at the approach of cold weather, although a few spend the summer here and rear their young. They are less timid than the snow bunting, and may often be approached quite close.

These two species form about all the attraction to be found to any extent in the fields, and, aside from an occasional hawk, only one more species frequents them, a species that is worth going miles to see—the snowy owl.

These birds reach us about the last of November and remain until the last of February, frequenting the neighborhood of some body of water, and seldom straying from it more than a mile or two. To see them and become at all acquainted with their habits, one must face all kinds of weather, possess untiring energy, and must undergo a considerable amount of fatigue. He will find them in the open country (as they frequent such ground altogether, seldom, if ever, entering the woods), perched on some fence post or stump, where, if undisturbed, they will remain for a considerable length of time, intently watching for mice, of which their food largely consists, set off by an occasional rabbit. They are extremely rare. One may tramp the fields for several days without success, and then again find one the first hour out.

On December 20, 1886, the writer started on a trip to Oneida Lake, N. Y., intending to devote his attention entirely to these birds; was gone four days, and saw five birds. This, of course, was exceptional, but shows what may happen.

In the dense pine and hemlock swamps several other species of owls are found, which are much more numerous at this season than in the summer. These are the long eared and short eared owls, with an occasional barred owl; but the most interesting of all is the Acadian or saw-whet, one of the smallest of the family and little known. It is far from common, being met with only at intervals. Its note, which closely resembles the filing of a large saw, occasionally betrays it; while at the same time it has a tendency to stray into barns and out-buildings, thus affording an opportunity for capture.

As it is not generally known, a description may be of some benefit. "Upper parts, including wings and tail, uniform chocolate-brown, spotted with white; under parts white, thickly streaked lengthwise with the color of the back; face, white."

In general appearance, they are the same as all owls, but when seen in the woods have a somewhat comical appearance, owing to their wise look for so small a bird.

We have often heard of the shrikes, or butcher birds, that capture small birds and impale them on the thorns of bushes. Many of us have wished to see them, and wondered where and when they were to be found. Now is the time. Any clump of bushes or young second-growth is a likely place to find them, for there are two species which visit us every winter and frequent these places. These are the great northern and loggerhead shrikes, the latter being most common; both bear a general resemblance, but differ mainly in size and in markings on the under parts. One can find them almost any day, perched on the topmost branch of some tree or bush, steadily eyeing the surrounding bushes in search of some victim, while on a thornbush near by will be found numberless moles, mice, and an occasional bird, awaiting the appetite of the marauder.

Aside from the goldfinches, many other birds of different species, instead of migrating with the rest, remain behind, and are to be found, on almost any pleasant day, in the warmer and more secluded parts of the swamp. Among these are the robin, golden-winged, downy, and hairy woodpeckers, the white-bellied nuthatch, and chickadees. These last are, perhaps, the most numerous of all our winter birds; whole flocks roam from one end of the swamp to the other, and I think there is no pleasanter sound to be heard in the woods in winter than to hear their clear "chick-a-dee-de-de-de" from a score of little throats, or to see them clinging to the branches and acting as familiarly as though no one was within sight or hearing. An occasional meadow lark will be flushed from the tall grass in some sheltered spot, while on the open streams will be found black ducks and mallards, whistlers and mergansers of two species, the hooded and buff-breasted or common sheldrake.

Truly, then, with all this material awaiting us, the fields and forests will be found inviting, and you who have never traversed them in winter do so now, and get a new interest awakened in them.

Itis not long since we spoke of the benefits conferred on the farmer by the inventor. The following statement is a good illustration of our views as then presented. It is taken from our contemporary, theNew England Farmer. "By the use of mowing machines and horse rakes and a horse hay fork, two boys in Connecticut last summer cut, raked, and helped to stow away 100 tons of hay, while their father was disabled from work by illness. Under such conditions a farmer is apt to feel like blessing the man who invents labor-saving machinery."

The action of this instrument is due to the facility with which liquids evaporate in a vacuum. A small amount of heat is sufficient to vaporize the liquid to the extent required to secure the desired action. The instrument is provided with a glass tube bent twice at right angles, and having a bulb blown on each end. The tube and the bulbs are partly filled with water, and a vacuum is secured by boiling the water in the bulbs before sealing them. The center of the tube is furnished with V-pivots, which rest in bearings in the top of the forked column. The column also supports a metal screen, which is bright one side and black on the other. Two pins project from the shield, to limit the movements of the glass tube and bulbs.

When the instrument is in use, the screen is placed toward the source of heat, and when radiant heat strikes the bulb which is unshielded by the screen, the water in that bulb is vaporized, and sufficient pressure is produced to drive the water upward into the bulb behind the screen. When a little more than half of the water has been in this manner forced from the lower to the higher bulb, the upper bulb preponderates. The tube and bulbs are supported on their pivot so as to secure unstable equilibrium, so that, when the upper bulb begins to descend, it completes its excursion at once, and exposes the full bulb to the radiant heat, at the same time carrying its empty bulb behind the screen, where it cools. The transfer of the water from the full bulb to the empty one now occurs as before. This operation is repeated so long as the bulbs are exposed to the action of radiant heat. The oscillations may be quickened by smoking the sides of the bulbs remote from the screen, and still greater rapidity of action may be secured by concentrating the heat on the bulbs by means of condensers or reflectors.

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