FIG. 3. ROTALIA ORNATA.FIG. 3. ROTALIA ORNATA.
FIG. 3. ROTALIA ORNATA.
These tiny creatures have been so numerous way back in the early ages of the world, that entire strata of rocks, several feet in thickness, in various parts of the world, are made up of their skeletons. The city of Richmond, Virginia, is built over rocks, composed largely of the minute fossils ofDiatomaceæintermingled with theForaminiferaand others.
A single prepared slide of these fossils will afford entertainment for an entire evening, so great is the diversity of form and so many hundreds on one slide. The Bahama Islands furnish the finest specimens of these fossils. The slides can be procured of any large dealer in optical instruments, or, what is still better, the young microscopist can soon learn to prepare them for himself, as ample directions are given in the books on the microscope.
In bidding my young readers adieu I shall not lose entire thought of them, but often when I am engaged in looking through the microscope, I shall think and ask myself, "Are they, too, absorbed in this pleasant work, and how many will become true workers and original investigators in this great field?" We shall all know in due time, for no earnest worker in any branch of science can long remain unknown. He will be found out sooner or later. A devoted student in microscopy will become so happy over the marvellous creatures and their curious ways that he cannot keep his pleasure to himself.
PART III
A HOME-MADE MICROSCOPE,AND HOW TO USE IT
By Frederick LeRoy Sargent
XIII.—HOW TO SEE A DANDELION.
A simple microscope, some mounted needles, a sharp knife and a pair of small forceps, are the only things needed to begin with.
There are many kinds of simple microscopes sold, some of which are of moderate price and answer every purpose; but if one has a little mechanical skill the cheapest way is to buy a magnifier and make the rest of the microscope one's self. What is known as the "bellows pattern," with three lenses, is one of the best of the cheaper forms of magnifiers, and is an admirable little instrument.
FIG. 1.
FIG. 1.
Fig.1 shows a home-made microscope ready for use. It will be seen that the main part consists of a wooden box having a hole in the top and open in front. To the back is attached a cork by means of a piece of thin metal as shown infig.2. Through this cord slides a rod on which slides another cork. A piece of brass wire has one endwound round the upper cork while the other end projects as an arm at right angles to the rod, and this projecting end sharpened and upturned, passes through holes drilled in the handle of the magnifier, and thus supports it. The lenses are focused,i. e.brought to the right distance from the object viewed, by sliding the cork up and down on the rod.
The object rests on a piece of glass laid over the hole in the top of the box. A piece of wood covered with white paper and placed below the object at an angle of about forty-five degrees answers for a reflector to illuminate those objects through which the light can pass. The pure white surface is better for the purpose than a mirror.
FIG. 2.
FIG. 2.
The most delicate part of the construction is making the holes in the corks for the rod to slide through. This may be done perfectly, however, by making the holes with a rat-tail file, trying the rodnow and then until it moves just right. The best thing for the rod is a piece of brass wire one quarter of an inch thick; a lead pencil however is a good substitute. Before bending the end of the brass wire arm it is well to heat it red-hot at the point of bending, to take out the temper: as otherwise it may break. The holes in the handle of the magnifier should be drilled as near the front as possible and so arranged that when the magnifier is in position the smallest lens will be near the object.
FIG. 3.
FIG. 3.
The mounted needles are shown infig.3. One pair of each kind will be enough to start with. To make one, take a fine needle, break off about a third, so it will not be too long and springy; then with a pair of pincers force it into the handle point first, withdraw it and finally force it in again with the point out. It may be easily bent with the pincers by first heating it to redness in a flame. When bent, heat it red once more and plunge quickly into water to re-temper it. Rubbing on an oil stone maybe necessary to remove roughness. Should the handles show any tendency to split, it would be well to wrap the end tightly with waxed thread.
The forceps (fig.4) may be purchased either of brass or steel at no great expense. Although not necessary it is more convenient to have them curved than straight.
FIG. 4.
FIG. 4.
If the reader will carefully follow the directions given below and endeavor to see for himself all the parts spoken of, he will probably have very little difficulty afterward in the use of the instruments just described; and the enjoyment he will have when he has learned how to examine little things, will amply repay for careful and persistent efforts at the start. Get a Dandelion in full bloom and also one that has gone to seed.
Have the microscope and the other instruments ready for use. The best place to work is on a table in front of a window where there is plenty of light, but not the direct rays of the sun.
Now cut the blossom in halves from the stem up. It will be seen that the stem is hollow and ends above in a cushion-like expansion. From the upper surface of this grow a number of little flowers, while from the sides there sprang two rows of little green organs that enclose the flower cluster like a cup. Remove one of the flowers with the forceps and place it in a drop of water on the glass stage of the microscope. Examine with one and one half inch power.[A]
Be careful to get just the focus. You are now ready to see the general form of the flower. At the base is a little body with roughened sides and slightly narrowed above (the ovary). Springing from the top of the ovary are a number of fine bristles (the pappus). Inside the bristles is a yellow portion, tubular below and flat above (thecorolla). Projecting from the tube of the corolla is a little yellow rod (the top of the stamens joined together); and coming from among the stamens are two slender recurved organs (the stigmas).
Now take a mounted needle in each hand and holding one needle on the flat part of the corolla split open the tubular part with the other. By keeping the lower part spread open with the needles, you will see that a number of delicate yellow threads grow from the sides of the corolla and are connected with the yellow stamen rod. These threads are another part of the stamens. In the middle of the flower is a single thread-like organ (the style) which comes from the top of the ovary and passing through the stamens projects beyond them, divided into two stigmas.
Most of my readers have probably studied enough botany to know the names of the different parts of a flower, but very likely many of them do not recognize the parts of the Dandelion flower as looking anything like the parts of the flower with which they are familiar.
Before proceeding further, therefore let us takea Morning-Glory flower—which you all know and can easily obtain, or at least some flower like it—and let us see that the parts of the two correspond.
Commencing in the centre we find in both a pistil, consisting of an ovary at the base and a stigma at the top and a style between. In the Dandelion the stigma is split in halves, while in the morning-glory it is not split but has three little knobs. Around the pistil come the stamens in each case. Each stamen is composed of two parts: a slender stem (the filament) and a little sac at the end (the anther) which is filled with pollen dust. In both cases the filaments grow out of the sides of the corolla. But while in the Morning-Glory the anthers are entirely free from one another, in the Dandelion they are joined together by their sides and form a tube around the style. The corolla in both cases is all of one piece, but in the Dandelion it is as if the upper part of the corolla were split open one side and then made flat. Instead of a green calyx as in the Morning-Glory, the Dandelion has a number of delicate white bristles. And, finally, in the Morning-Glory both the calyxand corolla grow out from below the ovary, while in the Dandelion its calyx of bristles and its corolla issue from above the ovary. So after all, you will see that corresponding organs are in both, and the difference between the two flowers is not so great as one might think at first.
Let the different parts of the Dandelion be examined now more minutely. First take some of the bristles and examine them with one quarter inch power. They are not perfectly smooth, but are more or less saw-like on the edge. With the same power look at other parts of the flower; notice the hairiness of the stigmas, the pollen grains coming out of the anthers (some grains may be found on the stigmas) also the roughness of the ovary and the delicate ribs or veins in the corolla. Examine one of the seed-like fruits with one and one half inch power. It is a ripened ovary. Compare the fruit with the ovary of a flower. The nutlet has become hard, rougher and more strongly ribbed. The narrowed upper part of the ovary has become much elongated and the pappus is spread out like an inverted umbrella.
Examine some bristles with one quarter inch power. They show the saw-like edges much more developed than in the younger bristles of the flower. We see throughout a beautiful adaptation of every part for fitting the little parachute to be carried long distances by the wind and finally to catch on some suitable place in which to sprout.
XIV.—HOW TO SEE A BUMBLE BEE.
You will first need to catch your Bumble Bee. A little chloroform poured on one will kill it instantly. Make a general examination at the outset of the insect. The outside of the body is horny and covered thickly with hairs. On the upper side the hairs are much more numerous than on the under side. The whole body is divided into three regions: the head, bearing the feelers and mouth-parts; a middle part (thorax) bearing the four wings and six legs; and a hind part (abdomen) armed with the sting.
Remove the head and examine with one and one half inch power. At the sides are two prominent oval bodies (compound eyes) which seem to be crossed by five lines; near the top of the head, between the compound eyes, are three little shiny bead-like organs (simple eyes); starting from about the middle of the face are the two feelers (antennæ)and at the lower part of the head are the mouth-parts. The sides, top and front of the head are all covered with hair.
Examine one of the compound eyes with one fourth inch power. The surface is made up of innumerable little facets, something like a cut diamond.
Cut off a piece of one of the compound eyes, remove some of the black pigment on the back and examine the piece in a drop of water. Each facet is a tiny hexagon. Some care is necessary to see them well.
Remove an antenna and examine it with three fourths inch power. It is thickly covered with minute hairs which give it a velvety appearance. Count the joints. At the base is the longest joint; at the lower end of which is a little knob that fits into a socket in the head. The next joint is quite small while those beyond are much alike.
Scrape the hairs from the face and examine the horny shell with three fourths inch power. The surface is full of little pits. In the upper part of the face there is a groove, in the middle of whichis one of the simple eyes. Just below the antennæ sockets is a groove which extends crosswise a short distance on either side and then bends downwards to the mouth. The portion of the face bounded by this groove is called the clypeus. At its lower part is hinged a little oblong piece (labium) which may be moved up and down with a needle.
Melt a piece of sealing wax on the centre of a slip of glass (taking care not to break the glass by too sudden heating) and before the wax hardens press the head into it face downwards.
Examine with one inch power. The hole near the top of the head shows the position of the neck. The portion of the head around this hole is destitute of hairs and is hollowed in, to make room for the rounded front part of the thorax. Below this one there is another cavity which contains a portion of the mouth parts when they are retracted. At each side of the mouth in front of the base of the sucking organs, are the two jaws (mandibles) each with a little tuft of hair on the outer side. The jaws move freely to and from each other, sideways instead of up and down as do the jaws of the higheranimals. The sucking apparatus consists of five pieces viz: two outermost pieces each tapering to a fine point, two, each of which ends in three little joints and one in the centre which projects beyond the others. It may be necessary to spread these out with the needle, to see them well.
Separate the thorax from the rest of the body. Scrape off the hairs on the back. Two principal grooves extend across the back, one near the front and one near the hind margin. The thorax is composed of three divisions and these grooves show where they are joined together. The hind division bears the hind wings and the hind pair of legs; the middle division, much the largest division of the three, bears the fore wings and the middle pair of legs; and the foremost division is quite small and bears only the front pair of legs.
Remove the wings of one side and examine in a drop of water with one and one half inch power. The wings consist of a shining transparent membrane strengthened by numerous horny veins running through it. Examine with one half inch power. The membrane is seen to be covered withminute hairs and little dots. On the front edge of the hind wing a short distance from the outer end is a row of hooks. At a corresponding place on the hind edge of the fore wing there is a thickening or ridge. When flying, the hooks catch onto the ridge and thus the wings are held together and act as one large wing.
Examine this grappling apparatus with one fourth inch power and with the needles hook the wings together and pull them apart. If you look through the magnifier while you do this you will get a good idea of the form of the ridge and of how the hooks catch onto it. Remove one of the forelegs, being sure that none remains attached to the body. Examine with one and one half inch power. The extremity is armed with two claws; then come four short joints followed by one about as long as the others together. All these make up the foot. The next joint above is the shank, then comes the thigh and then quite a small joint, the lower hip, and lastly attached to the body is the upper hip.
Remove the last five joints of the foot (the claw part, and the other four joints) examine with onethird inch power. The claws have each a branch projecting from the inner edge. Between the claws is a little velvety pad. Each of the small joints is covered with short closely appressed hairs and from the lower end of each joint project several spines. Now examine the remaining long joint of the foot attached to the shank. At the upper end of the inner side is a deep semicircular notch, the upper portion of which is light colored. Beside the notch is a peculiarly shaped movable spine which projects from the lower end of the shank. This queer arrangement is what the bee uses to clean his feelers. The reader has probably seen the operation performed by a bee or a wasp. The leg is thrown over the feeler, the latter is grasped at that particular bend of the leg where the cleansing apparatus is situated and then drawn through from base to tip; and this is repeated several times with each feeler.
Examine with one and one half inch power a leg from each of the other pairs and compare the corresponding parts. They differ chiefly in size and in the absence of the cleansing apparatus. Youcannot fail to admire the many beautiful forms of the different portions. On the outer side of the hind shank is a smooth flattish surface destitute of hairs, excepting a fringe of long ones at the margin. At this place may sometimes be found a sticky mass of pollen intended for bee-bread. Examine the abdomen with one and one half inch power. It is composed of several wings. If some of the hairs are scraped off this will be shown more clearly. From the hind extremity projects the sting.
We have far from exhausted all the beautiful and interesting points in the make-up of a Bumble Bee, not even those that may be seen with the limited powers of a simple microscope; but probably enough has been said to show the reader that such things are well worthy of study and it is hoped that enough directions have been given to render future use of the instruments comparatively free from difficulty.
XV.—SOME LITTLE THINGS TO SEE.
There is no end to the beautiful and wonderful things one can see with the simple microscope. Only a few of the more attractive and easily obtained of these are now to be mentioned.
To begin with, there are ever so many pretty flowers to look at. The asterworts, that is, such flowers as the daisy, aster, golden rod, dandelion and thistle, are particularly full of beauty. The blossoms are all made up of a number of little flowers as in the dandelion; but the shapes and colors and so forth, of the different kinds are exceedingly various. Some, such as the asters and daisies, have two kinds of flowers in the same blossom—flowers with strap-shaped corollas (like the dandelion's) are arranged along the margin of the blossom, while in the centre are little flowers with star-shaped corollas presenting a much differentappearance. Flowers of many of the Parsley Family, for example wild carrot, wild parsnip and caraway, are quite odd. Very pretty flowers are found among the grasses, sedges and common weeds. The different trees as they bloom in spring—the maples, elms, willows, poplars, sassafras and hosts of others—all have flowers that are perfectly lovely. Most of these flowers need to be picked to pieces under the magnifier to show up their full beauty. The parts of flowers, both small and large ones, deserve attention. Frequently one meets with remarkable forms.
Seeds are highly interesting. They are often handsomely marked with series of pits or projections, grooves or ridges. One meets with many curious appendages by means of which the seeds are carried off and sown at a distance from the plant. Some, like the dandelion, have a parachute attachment; others have wings to catch the wind, and others still are covered with hooked spines whereby they become attached to the fur of animals, there to remain until brushed off onto the ground.
Leaves and stems sometimes have on them beautiful hairs and oil-glands. The wooly covering of common mullein, for example, is made up of innumerable slender-branched hairs. These show best when a piece of the leaf broken off is looked at edgewise.
If you examine the fruit-dots on the backs of the different kinds of ferns you will be surprised to find how pretty they are and of how many different shapes. Sometimes the fruit is not borne on the back of the leaf but forms little clusters by themselves, which are sometimes at the end of the fern, sometimes in the middle, sometimes on a separate stalk.
Mosses, lichens and sea-weeds are well worth looking at.
Early in the summer an exquisite little fungus called "Cluster cups" may be found on the underside of barberry leaves. Hawthorn and other plants have handsome fungi on them later in the season.
By observing closely while out in the fields or woods, one sees hovering about in swarms, myriadsof tiny insects. Under the lens some of them are very odd, others very beautiful. The easiest way to catch these little midgets, is to wet the palm of the hand and then sweep it among them, or in the same way use a piece of sticky paper.
The study of the different parts of insects is one of the most fascinating of the many uses of the Simple microscope. Although all insects are made up on the same general plan and corresponding organs occur in most of them, there is an endless variety in the forms under which we see the different organs and the uses to which they are put.
Take for example the antennæ. In the grasshopper it is long and threadlike; in the butterflies always ending in a knob; in moths always tapering to a point, although sometimes threadlike and sometimes much branched, forming a beautiful plume; in the beetles, sometimes fan-like, sometimes like a comb; and in other insects assuming still other forms. Insects' eyes are often colored beautifully. A horse-fly's eyes are striped. Butterflies' eyes have usually a soft liquid coloring, and moths' eyes in the dark shine like little fiery beads.
The mouths of insects, such as beetles, grasshoppers and dragon flies, have strong jaws for biting; flies, bugs, moths and butterflies, have the mouth-parts transformed into sucking organs, while bees, wasps and the like have both sucking organs for honey, and biting organs for leaf-cutting, wood-tearing etc. as we saw was the case in the Bumble Bee.
Butterflies' wings and moths' wings are covered with little scales of a variety of shapes. These should be examined attached to the wing to show their arrangement which is like that of shingles on a roof; but to show their form they should be looked at when brushed from the wing onto a piece of glass. Many other peculiarities may be noticed in the wings of other kinds of insects.
Legs, the same as the other organs, have various forms, markings and appendages, and so it is with the abdomen and its stings or its egg-laying apparatus.
The hairs of "Wooly Bears" and caterpillars of that kind are peculiarly branched.
The four hind pairs of feet in caterpillars arearmed each with a row of little hooks which are used in walking to get a firm hold. The larger caterpillars show the hooks best.
Sometimes you will find pretty insect eggs on the underside of leaves or on stems, and also little silken cocoons in similar places. If you are near a pond-hole, or an old hogshead that collects rain water, you can find a good many little animals, some of them very frisky—young mosquitoes or "polywogs," water-fleas, cyclops, little worms, young dragon-flies and lots of others. When you go to collect them take a small wide-mouth bottle and, having found a place where there is what you want, lower your bottle, mouth down, in the midst of them and when it is well under water turn the mouth upwards. A good many of the animals will run in with the water. If the first time you do not get what you want, the second time you may. When you want to examine them at home you can fish them out with a glass tube and put them in a watch crystal or on the glass stage of the microscope. In using the tube take it between the thumb and middle and third fingers, and close the top withyour first finger; then put the lower end of the tube in the water close to the thing you want to catch; now lift your first finger quickly and the water will run in the lower end of the tube carrying with it your little squirmer, unless he has been too quick for you. Close the top of your tube again and the water will not run out when you remove the tube, until you lift your finger. Sometimes it takes a good deal of patience and skill to catch the more agile of the little water animals. Glass tubes are sold in drug stores for five or ten cents.
If you begin by examining the objects already spoken of, you will while looking for these be continually discovering for yourselves new objects possessing new beauties and will soon see that not half the interesting things you can find have been ever hinted at.
The way to find out about all these things is to go out into the fields and woods, and form the habit of observing closely what is around you. Carry your magnifier along and look at this flower, that fern, this insect, that moss, with different powers of the magnifier; and when you comeacross any objects worthy of a more careful examination carry them home and examine them systematically with Simple microscope, needles, knife, and so forth. Insects may be kept well in alcohol until winter, and then careful studies may be made of them.
When using the magnifier in the field, hold it in such a way that the smallest lens will be nearest the object when the lenses are combined and be careful not to shade the object with the hand or the hat brim. Just enough light should fall on the object to make its examination comfortable for the eyes. If you rest the hand holding the magnifier on the hand that holds the object, both lens and object can be held much steadier. When commencing to examine an object it is best to have the three lenses spread apart, for in this way you can use first the lowest power then those higher and finally, if you wish to, the three lenses combined. The dissecting forceps are very handy to have in the field, both for picking up anything too small for the fingers and for holding an object to be examined.
A collection of some of these little things preserved and ready for examination adds greatly to the pleasures of studying them. Of course all the different kinds of objects cannot be preserved so as to show their full beauty, but many can be and the following directions will tell how to make a very good collection:
Seeds, fern-fruit, insects and other opaque objects like these may be mounted on pasteboard slides. One of these slides consists simply of a stout piece of pasteboard, having a hole cut in the centre and a piece of thick paper or cardboard glued on the under side. The object is attached to the cardboard at the bottom of the hole.
It is best to make a number of these slides at a time. Having procured some quite thick pasteboard, from old paper boxes, rule lines on the surface dividing it up into spaces three inches long by one inch wide. In the centre of each space cut out a hole about half an inch in diameter. A sharp knife will make a neat square hole or a good round one may be made with a gun-wad punch. This done, the spaces may be cut apart with a sharp knife andruler, along the lines already drawn. Pieces of cardboard for the backs should be cut a trifle larger than the pasteboard portion of the slide; after they are glued onto the latter they may be trimmed down neatly with a pair of scissors. Glue or mucilage containing glycerine (in the proportion of one or two teaspoonfuls to an ordinary bottle of mucilage) is the best thing to use for sticking on the backs. While the slides are drying they should be either under a weight or in a clamp screwed up tightly, so as to prevent their twisting out of shape. The mucilage may be prevented from being squeezed in round the edges of the hole, by taking care when putting it on not to have it come too near the hole. One or two coats of India Ink may be painted on the middle of some of the pieces of cardboard, either before or after they are put onto the slides; and thus a black background may be obtained for the lighter-colored opaque objects. Many of the objects will however show best on a white background.
When you have the slides all made, nothing more is needed to mount an object, than simply toattach it to the bottom of the hole with a little mucilage and glycerine, or something of that sort, and finally to write the name of the object on the front part of the slide, and on the back any desirable notes. A good way to mount such objects as fine seeds is to put them in the hole loosely and then cover them with a piece of mica such as will be spoken of presently.
Objects which are to be examined by the light shining through them, for example a bee's wing or a butterfly's scales, must be mounted on glass slides.
A glass slide three inches by one is taken, on the centre is placed the object; over this is laid a thin piece of clear mica three fourths of an inch square, and this is attached to the glass by pasting narrow strips of tissue paper around the edges of the cover, partly on the cover and partly on the slide. Finally the slide is covered with some pretty colored paper and labeled.
Two pieces of paper are needed to cover each slide. One for the under part is cut about one and one half by three and one half inches, with a hole in the centre (round or square). This pieceis first pasted on, the corners being cut and the edges brought over onto the front. The upper piece, which has a hole in the centre similar to that in the lower piece, and is cut a trifle larger than the three by one inch slide, is next pasted on so that the hole will correspond with the one below. The upper piece of paper is now trimmed down to the slide and the label attached. Window glass will answer for the slides and you can get any glazier to cut up a piece for you into the right-sized slips. Mica can be bought at a stove store, in sheets which may be cut up into three fourths of an inch squares with a pair of scissors. The mica should be as clear as you can get it. You will find it handy to have some tissue paper all mucilaged like postage stamps and cut up in strips the right size ready to use. The same may be said of the colored paper covers and the labels.
The dust may be excluded from the uncovered opaque objects by keeping the mounted slides in small groups, held together by elastic bands. This will also serve to classify them so that all the insects will be together, all the seeds, and so on; andthe transparent slides may also be treated in the same way. When an elastic band wears out, it is no great trouble to replace it.
In working with the Simple microscope there is a fine chance to display ingenuity, not only in making the instruments and mounting the objects but in discovering new things to look at and in seeing how much can be found out about those things which are the most common.
FOOTNOTE:
[A]In these directions "11⁄2in.power" means a lens having a focus of 11⁄2inches; "1⁄2in.power" means a lens or combination of lenses having a focus of1⁄2inch; and so on. All the different powers mentioned in the directions may be obtained in the small-sized 3-lens, bellows form magnifier, either by using the lenses singly or combined in different ways. The magnifying power of any single lens or simple combination is easily found by dividing 10, by the focus in inches. Thus the magnifying power of a1⁄2in.lens is found in this way: 10÷1⁄2= 10×2⁄120. The lens magnifies therefore 20 diametersi. e.makes an object appear twenty times as long and twenty times as broad as it is.
[A]In these directions "11⁄2in.power" means a lens having a focus of 11⁄2inches; "1⁄2in.power" means a lens or combination of lenses having a focus of1⁄2inch; and so on. All the different powers mentioned in the directions may be obtained in the small-sized 3-lens, bellows form magnifier, either by using the lenses singly or combined in different ways. The magnifying power of any single lens or simple combination is easily found by dividing 10, by the focus in inches. Thus the magnifying power of a1⁄2in.lens is found in this way: 10÷1⁄2= 10×2⁄120. The lens magnifies therefore 20 diametersi. e.makes an object appear twenty times as long and twenty times as broad as it is.
TRANSCRIBER'S NOTES:
Inconsistencies in hyphenation have been retained from the original.
Obvious typographical errors have been corrected as follows:
Page 8: hundreth changed to hundredthPage 11: iustrument changed to instrumentPage 15: diferent changed to differentPage 17: he changed to thePage 20: wil changed to willPage 44: or changed to ofPage 72: staightened changed to straightenedPage 86: DIFFRENT changed to DIFFERENTPage 125: fouths changed to fourths