Fig. 5—SOEMMERING'S FIRST TELEGRAPH.
Fig. 5—SOEMMERING'S FIRST TELEGRAPH.
In 1811, Soemmering simplified his apparatus as regards the number of signs. Instead of having 25 letters (a complete alphabet minusx) and 10 figures, he did away with these latter and the letter J, and introduced thex, the period, and a sign of repetition. The apparatus was thus reduced to 27 wires.
The first experiments in telegraphy made with this system, on the 9th of July, 1809, were over a distance of 38 feet; on the 19th, transmission was effected to 170 feet; and, on the 8th of August, to 1,000 feet; but it was not until he had perfected the insulation of his wires by means of India rubber dissolved in ether, and had devised his paddle-wheel call, that Soemmering decided to present his telegraph to the Academy of Sciences of Bavaria during its session of August 28, 1809.
Some time afterward, Baron Larrey, Inspector General of the medical service of the French armies, carried Soemmering's telegraph to Paris and presented it to the Academy of Sciences at its session of December 5, 1809. This presentation gave rise to a series of letters addressed by Soemmering to the Baron. His son, now a member of the Academy, has had the goodness to communicate these to Count du Moncel, through whose kindness we are enabled to cite the most interesting passages from them.
Soemmering writes on the 10th of November:
"I have the honor to remit to you herewith a memoir which, conjointly with the trifles that you have had the goodness to charge yourself with, will explain my meaning clearly and briefly. I am desirous of learning the reception that His Imperial Majesty deigned to accord to these ideas. The memoir, as you will see, sir, makes mention, aphoristically, of a few quite varied experiments that I have been in a position to perform. I dare to flatter myself that they will please several members of the Institute. Independent of the major interest of which they seem susceptible, that of novelty belongs to them. In my opinion, there is no one who can dispute it...."
On the 5th of December, 1809, as we have said, the telegraph was presented to the Institute, but the inventor does not seem to have been at once informed of it; for he writes, under date of July 30, 1810:
"I have, sir, read your dissertation upon my telegraph with great pleasure.... Has my succinct memoir on the telegraph, sent from here on the 12th of November, reached you, sir, and have you had the goodness to communicate it to the Institute?
"As the old wires that were pretty badly treated by many manipulations had really suffered therefrom, and as it was only to save time that I did not have them renewed before sending the apparatus, I wish that they could be replaced by ordinary clavichord wires wound with silk, inasmuch as the material in these is more durable than the copper of the old ones. Had I been able to flatter myself, sir, that you would have taken enough interest in this invention to be at the trouble of carrying it to Paris, I should certainly not have failed to effect in advance this small and necessary improvement, which, leaving time out of consideration, will require but a care as to details. For, in fact, I strongly apprehend that not only the brittleness of the copper wire, but also the violence that trials anterior and even foreign to present use have submitted these wires to, have possibly got the silk out of order, or used it up here and there, thus producing immediate contacts of metal and bringing about a premature closing of the galvanic chain, whence would result a total disarrangement of the questions. I truly regret, then, having (through being too jealous of time, which you yourself know so well the value of) sent you the instrument in such a state of imperfection, and I cannot do better than ask to have it sent back here in good order. Permit me, then, to ask you at once to please not let Prince de Neufchatel nor even His Majesty the Emperor see it until the said repair has been effected, either by myself or (if the sending back would seem to you to take too long) by some one of our skillful artists at Paris. According to my convictions, there is but this means of preventing its effect from failing us, even for ever. It is a true pleasure to see it so infallible and complete as it is in the new instrument of absolutely the same structure that I have had constructed for the Academy of Munich."
The telegraph, which doubtless was repaired at Paris, was returned to Munich only in May, 1811. The same year it was carried to Vienna by the Russian Count Potocki, whom Baron Schilling had made known to Soemmering, and who presented the apparatus to Emperor Francis the First, on the 1st of July of the same year. Another model was sent by Soemmering to his son William, then at Geneva, who showed it to Augustus Pictet, to De la Rive, and to some other savants.
Despite all such presentations no high personage showed himself disposed to aid Soemmering in making an extended application of his invention. The committee named by the Academy of Sciences, and in which figured Monge, Biot, and Carnot, does not seem to have made any report. The apparatus was considered of small importance alongside of that of Claude Chappe, and Napoleon himself, says Mr. Zoellner, treated the invention as a German vision. On another hand, Bavaria and Austria showed just as little enthusiasm; but Soemmering, reduced to his own resources, continued his experiments none the less on that account. On the 4th of February, 1812, he found it possible to telegraph to a distance of 4,000 feet, and on the 15th of March of the same year he operated his apparatus with complete success over a line 10,000 feet in length.
This was certainly making great progress; but it is certain that, even if Soemmering had not encountered universal indifference, his telegraph would not have been able to become practical, because of the large number of wires employed. A modification, however, would have enabled it to play a role during the twenty-five years which preceded the invention of more easily realizable systems. This modification is the one Salomon Christopher Schweigger proposed in an appendix to the memoir of Soemmering inserted by him in 18115in his journal, thePolytechnisches Central—Blatt.
His proposition was that two unequal piles should be employed instead of one, so that first one and then the other, or even the two combined, should act; and, besides, that the number of wires should be reduced to two, in taking into consideration the time during which the gases were disengaged, as well as the interruptions of varying length, and to which would succeed the action, first of the larger, and then of the smaller pile. With these different modifications, it certainly would have been possible to employ but two wires, and to render the laying of the wires less costly.
After Soemmering, we may cite in the same category John Redman Coxe, who, according to a note inserted in 1810 in theAnnals of Philosophy, proposed to utilize for telegraphy the decomposition of water or metallic salts. Coxe, however, does not seem to have ever made any experiments.
In 1814 John Robert Sharpe claimed likewise to have made experiments in telegraphy in 1813; and these in all probability were based upon electro-chemical action.
Upon the whole, the only important one of these electro-chemical apparatus is that of Soemmering. This marks an epoch in the history of electric telegraphy, but it was not capable of the extension that can be given the apparatus based upon Oersted's discovery.
Fig. 6.—SOEMMERING'S PERFECTED TELEGRAPH.
Fig. 6.—SOEMMERING'S PERFECTED TELEGRAPH.
To be continued.
Some studies made of the telegraph service of the Railway Company of the East (France) have resulted in a happy modification of the Callaud pile, rendering it easier of maintenance and reducing the consumption of the materials employed.
As well known, the Callaud pile, which is exclusively employed for telegraphic purposes by certain railroad companies, consists of a glass vessel, of a circular piece of zinc suspended by hooks from the upper part of the vessel, and of a strip of copper resting on the bottom of the latter. This copper strip is riveted to a rod of the same metal which constitutes the positive electrode. In the bottom of the vessel there is placed a saturated solution of sulphate of copper, so that its level reaches to within a short distance of the lower part of the zinc, and the vessel is then filled with pure water. The zinc being attacked, there is formed a zinc sulphate, which always remains at the upper part ofthe vessel by reason of the difference in density of the solutions of sulphate of zinc and sulphate of copper, and the reduced copper deposits upon the strip in the center. It has been found necessary to cover the copper rod with a sheath of gutta-percha in order to keep it from being cut at the line of intersection of the two liquids, and this is the first inconvenience of the system. It is necessary, moreover, to keep the solution of copper at a certain degree of concentration by placing in the bottom of the vessel a supply of crystals of sulphate of copper. Hence it happens that the solution, being increased, eventually reaches the zinc, and the latter is thereupon attacked to no purpose, with a pure loss of copper through reduction. This is a second inconvenience, which can be remedied by introducing into the pile only a simply saturated solution without excess of crystals. It will be seen that, in this latter case, it is necessary to visit the pile quite frequently, to empty it by means of siphons, and to confide its maintenance to experienced persons only.
This is why, up to the present, railroad companies have preferred the Daniell to the Callaud pile for alarm bells that control signal disks, despite the serious advantages of the Callaud pile and the inconvenience of the porous vessel that enters into the composition of the other.
NEW SULPHATE OF COPPER PILE.
NEW SULPHATE OF COPPER PILE.
The modified Callaud pile is exempt from the defects that we have just pointed out. It differs from the old form in the substitution of a leaden tube, open at its extremities and dipping into the liquid of the pile, for the piece of copper or positive electrode. The lead, which is not attacked, and may serve indefinitely, is held in a vertical position by means of a foot made by cutting slits with a pair of scissors in the bottom of the tube, and bending back the strips thus formed. This foot also serves to prevent the tube from touching the zinc, by holding it in equilibrium.
In order to charge the element thus constituted, it is only necessary to fill the lead tube with crystals of sulphate of copper and to pour water into the glass vessel until its level reaches within a centimeter and a half of the upper edge of the zinc. In an hour the copper will have dissolved sufficiently to allow the pile to begin its action.
Experience has demonstrated that, whatever be the supply of copper that is put into the lead tube, the saturated solutionwill never reach the zinc, even in an open circuit.
In sum, the new arrangement given to the Callaud element presents the following advantages: (1) It permits of the maintenance being confided to anybody, since this consists simply in the introduction into the central tube of crystals of sulphate of copper when it is seen that the blue tint of the lower liquid is disappearing. (2) It permits of proportioning the expense to the work really effected.—La Nature.
SUGGESTIONS IN ARCHITECTURE.—ENGLISH LODGES.
SUGGESTIONS IN ARCHITECTURE.—ENGLISH LODGES.
Lodges, Portington Grange, Eastrington.Walter Hanstock, Architect.Ground Plan.Chamber Plan.
Lodges, Portington Grange, Eastrington.
Walter Hanstock, Architect.
Ground Plan.Chamber Plan.
The walls of the buildings are best scarlet pressed bricks with white tuck joints; the wood framing is stained brown-black and well varnished; the windows finished white; cement filling, flat cream white; and Broseley strawberry tiles for roof. The buildings are situated in the center of a plantation, and the combination of color is most satisfactory. They are built at the principal entrance to Portington Grange, Eastrington, near Hull, and belong to Thomas Brearley, Esq., J.P. The works have been carried out under the direction of Mr. Walter Hanstock, architect, Batley.—Building News.
The paper, which will be published in full by the Building Stone Department of the Tenth Census of the United States, considers the building stones employed in New York city and its suburbs,i. e., Brooklyn, Staten Island, Jersey City, and Hoboken.
The materials of general construction occur in the following percentage proportion to the total number of buildings in the cities stated in the table below:
In New York city proper, the several varieties of stone are used in the following proportion to the entire number of stone buildings:
In Brooklyn, the Connecticut brownstone is the variety predominating among the stone buildings (95.7 per cent.), and is employed almost altogether for the fronts of residences. Very few iron buildings occur, but over three times as many stucco fronts as in New York. The frame buildings predominate, particularly in the outskirts,e. g., Long Island City (80.5 per cent).
In Staten Island, stone enters in very small proportion into the fronts of buildings, though commonly employed, as in New York and throughout this district, for the dressing of apertures, the walls of inclosures, and other masonry.
In Jersey City, the proportions of the materials are much as in Staten Island. The selection of the dark trap from the Heights behind the city, for the construction of many fronts or entire buildings, is a local feature of interest.
In Hoboken, the same general features prevail as in Jersey City.
The annual reports of the Committee on Fire Patrol of the New York Board of Fire Underwriters, for the years 1881 and 1882, have yielded the following statistics, which, so far as they go, closely approximate my own:
The materials of construction for this district, which does not include the 23d and 24th Wards, north of the Harlem River, are reported as follows:
An exceedingly rich and varied series is brought to our docks, and the number and variety are constantly increasing. A few of the more important may be here mentioned.
Freestones (Carboniferous sandstone), commonly styled "Nova Scotia stone," or "Dorchester stone," in various shades of buff, olive-yellow, etc., from Hopewell and Mary's Point, Albert, N. B., and from Wood Point, Sackville, Harvey, and Weston, N. B., Kennetcook, N. S., etc. A very large number of private residences in New York and Brooklyn, etc., the fences, bridges, etc., in Central and Prospect Parks, many churches, banks, etc.
Freestone (Mesozoic sandstone), commonly styled "brownstone," from East Longmeadow and Springfield, Mass., but chiefly from Portland, Conn., in dark shades of reddish-brown, inclining to chocolate. This is the most common stone used in the fronts of private residences, many churches, Academy of Design in Brooklyn, etc.
Freestone (Mesozoic sandstone), "brownstone," from Middletown, Conn., Trinity Church, Brooklyn, etc.
Red sandstone (Potsdam sandstone), Potsdam, N. Y. Several residences, buildings of Columbia College, etc.
Freestone (Potsdam sandstone), "brownstone," Oswego, N. Y. Part of Masonic Temple in 23d Street.
Freestone (Mesozoic sandstone), "brownstone," in several shades of light reddish-brown, orange-brown, etc., and generally fine-grained, from Belleville, N. J. Very many of the best residences and churches,e. g., cor. 60th and 64th Streets, and Madison Avenue, etc.
Also, varieties of the same "brownstone" from Little Falls, N. J. (Trinity Church, New York), from the base of the Palisades (part of the wall around Central Park), etc.
Freestone (Lower Carboniferous sandstone), commonly styled "Ohio stone," from Amherst, East Cleveland, Independence, Berea, Portsmouth, Waverly, etc., Ohio, in various shades of buff, white, drab, dove-colored, etc. Many private residences and stores, the Boreel building, Williamsburgh Savings Bank, Rossmore Hotel, etc.
Freestone (Mesozoic sandstone), often styled "Carlisle stone," from the English shipping port, or "Scotch stone," from Corsehill, Ballochmile and Gatelaw Bridge, Scotland; in shades of dark red to bright pink. Fronts of several residences, trimmings of Murray Hill Hotel, the "Berkshire" building, etc.
Also, varieties from Frankfort-on-the-Main, Germany, etc.
Blue sandstone (Devonian sandstone), commonly styled "bluestone," from many quarries in Albany, Greene, Ulster, and Delaware counties, N. Y., and Pike county, Penn. The trimmings of many private residences and business buildings, walls and bridges in the parks, part of Academy ofDesign in 23d Street, Penitentiary on Blackwell's Island, house at 72d Street and Madison Avenue, etc.
Freestone (Oolite limestone), "Caenstone," from Caen, France. Fronts of several residences in 9th Street, trimmings of Trinity Chapel, the reredos in Trinity Church, New York, etc.
Limestone (Niagara limestone), Lockport, N. Y., Lenox Library, trimmings of Presbyterian Hospital, etc.
Limestone (Lower Carboniferous), styled "Oolitic limestone," from Ellitsville, Ind. Several private residences (e. g., cor. 52d Street and Fifth Avenue), trimmings of business buildings, etc.
Also, varieties of limestone from Kingston and Rondout, N. Y., Isle La Motte, Lake Champlain, Mott Haven, and Greenwich, Conn., etc. Part of the anchorages of the Brooklyn Bridge, walls in Central Park, etc.
Granyte, Bay of Fundy, N. S. Columns in Stock Exchange, etc.
Red granyte, Blue Hills, Me. U. S. Barge Office.
Gray granyte, East Blue Hills, Me. Part of towers and approaches of New York and Brooklyn Bridge, etc.
Granyte, Spruce Head, Me. Part of towers of Brooklyn Bridge, bridges of Fourth Avenue Improvement, Jersey City Reservoir, etc.
Gray granyte, Hurricane Island, Me. Part of New York Post Office and of towers and approaches of Brooklyn Bridge, etc.
Granyte, Fox Island, Me. Basement of Stock Exchange, etc.
Granyte, Hallowell, Me. Trimmings in St. Patrick's Cathedral, Jersey City Heights, etc.
Granyte, Round Point, Me. Seventh Regiment Armory, etc.
Granyte, Jonesborough, Me. Welles' building, panels in Williamsburgh Savings Bank, etc.
Granyte, Frankfort, Me. Part of towers and approaches of Brooklyn Bridge, etc.
Granyte, Dix Island, Me. New York Post Office, part ofStaats Zeitungbuilding, etc.
Also, varieties from Calais, Red Beach, East Boston, Clark's Island, Mt. Waldo, Mosquito Mountain, Mt. Desert, Ratcliff's Island, etc., Me.
Granyte, Concord, N. H. Booth's Theater, German Savings Bank, etc.
Granyte, Cape Ann, Mass. Dark base-stone and spandrel stones of towers and approaches of Brooklyn Bridge, etc.
Granyte, Quincy, Mass. Astor House, Custom House, etc.
Granyte, Westerly, R. I. Part of Brooklyn anchorage of Brooklyn Bridge.
Granyte, Stony Creek, Conn. Part of New York anchorage of Brooklyn Bridge.
Also, varieties from St. Johnsville, Vt., Millstone Point, Conn., Cornwall, N. Y., Charlottesburgh, N. J., Rubislaw, and Peterhead, Scotland, etc.
Gray gneiss, New York Island, and Westchester county, N. Y. A large number of churches, Bellevue Hospital, the Reservoir at 42d Street, etc., and the foundations of most of the buildings throughout the city.
Gray gneiss, Willett's Point, and Hallett's Point, Kings county, N. Y. Many churches in Brooklyn, the Naval Hospital, etc.
Marble, Manchester, Vt. Drexel & Morgan's building, church cor. 29th Street and Fifth Avenue, etc.
Also, many varieties from Swanton, West Rutland, Burlington, Isle La Motte, etc., Vt. The "Sutherland" building at 63d Street and Madison Avenue, residences at 58th Street and Fifth Avenue, etc.
Marble, Lee, Mass. Turrets of St. Patrick's Cathedral, etc.
Marble, Stockbridge, Mass. Part of old City Hall, New York.
Marble, Hastings, N. Y. The University building, etc.
Marble, Tuckahoe, N. Y. Part of St. Patrick's Cathedral, residence on the cor. of 34th Street and Fifth Avenue, etc.
Marble, Pleasantville, N. Y., styled "Snowflake marble." Greater part of St. Patrick's Cathedral, Union Dime Savings Bank, many residences and stores, etc.
Also, many varieties from Canaan, Conn., Williamsport, Penn., Knoxville, Tenn., Carrara and Sienna, Italy, etc.; used generally, especially for interior decoration, etc.
Trap (Mesozoic diabase), from many quarries along the "Palisades," at Jersey City Heights, Weehawken, etc. Stevens Institute, Hoboken, N. J., Court House on Jersey City Heights, old rubble work buildings at New Utrecht, etc., on the outskirts of Brooklyn, etc.
Trap (Mesozoic diabase), styled "Norwood stone," from Closter, N. J. Grace Episcopal Church, Harlem.
Also, varieties from Graniteville, Staten Island, N. Y., and Weehawken, N. J.
Serpentine, Hoboken, N. J. Many private residences, masonry, etc., in Hoboken. Also, varieties from Chester, Pa.
In addition to the edifices referred to above, many public buildings of importance are constructed of stone,e. g.: Prisons in the city and on the islands, bridges in the parks and over the Harlem River, in which sandstone, limestone, granyte, and gneiss are used.
The sewers are constructed of gneiss from New York Island and vicinity, as well as of bowlders of trap, granyte, etc., from excavations.
The Croton Aqueduct, the High Bridge, the Reservoirs in the Central and Prospect Parks and at 42d Street, in which gneiss from the vicinity and granyte from New England were used.
The walls, buildings, bridges, and general masonry in the parks are constructed of the following varieties of stone:
Freestone (sandstone), from Albert, Dorchester, and Weston, N. B.
Brownstone, from Belleville and the base of the Palisades, N. J.
Bluestone and "mountain graywacke," from the Hudson River.
Limestone, from Mott Haven and Greenwich, Conn.
Granyte, from Radcliffe's Island, etc., Me.
Gneiss, from New York, Westchester, and Kings counties, N. Y.
Marble, from Westchester county, N. Y.
The fortifications in the harbor and entrance to the sound, constructed of granyte from Dix Island, Spruce Head, etc., Me., gneiss from the vicinity, brownstone from Conn., etc.
The stonework of the New York and Brooklyn Bridge, as I am kindly informed by Mr. F. Collingwood, the engineer in charge of the New York approach, is constructed of the following materials:
Granyte, from Frankfort, Spruce Head, Hurricane Island, East Blue Hill and Mt. Desert, Me., Concord, N. H., Cape Ann, Mass., Westerly, R. I., Stony Creek, Conn., and Charlottesburg, N. J.
Limestone, from Rondout and Kingston, N. Y., also from Isle La Motte and Willsboro Point, Lake Champlain, and vicinity of Catskill, N. Y.
In the anchorages, the corner stones, exterior of the cornice and coping, and the stones resting on anchor plates, consist of granyte from Charlottesburg and Stony Creek, in the New York anchorage, and from Westerly, in the Brooklyn anchorage. The rest of the material is entirely limestone, mainly from Rondout, largely from Lake Champlain. In the towers, limestone was chiefly employed below the water line, and, above, granyte from all the localities named, except Charlottesburg, Westerly, and Stony Creek. In the approaches the materials were arranged in about the same way as in the towers. Additional particulars are given concerning the quantity, prices, tests of strength, and reasons for selection of the varieties of stone.
For roofing, slate is largely employed throughout these cities, being mainly derived from Poultney, Castleton, Fairhaven, etc., Vt., and Slatington, Lynnport, Bethlehem, etc., Penn.
For pavements, the bowlders of trap and granyte from excavations have been widely used in the "cobblestone" pavements. The trap (or diabase) of the Palisades across the Hudson, immediately opposite New York city, and from Graniteville, Staten Island, is used in the "Russ" and Belgian pavement; also, granyte from the Highlands of the Hudson, from Maine, etc, in the "granite block" pavement in both New York and Brooklyn; large quantities of crushed trap from Weehawken and Graniteville, for the macadamized streets and roads in the parks and outskirts; and also wood, concrete, and asphalt in various combinations.
For sidewalks and curbstones, the material generally employed is the flagstone, a thinly bedded blue sandstone or graywacke from the interior of the State, the Catskill Mountains, and from Pennsylvania; also, granyte, chiefly from Maine. In the older streets, a mica slate from Bolton, Conn., and micaceous slaty gneiss from Haddam, Conn., were once largely used, and may still be occasionally observed in scattered slabs.
Additional facts were given concerning the ruling prices for the varieties of stone, tables presenting all the determinations obtainable in reference to the crushing strength of the varieties used in New York, lists of the dealers in building and ornamental stones, etc.
All varieties of soft, porous, and untested stones are being hurried into the masonry of the buildings of New York city and its vicinity. On many of them the ravages of the weather and the need of the repairer are apparent within five years after their erection, and a resistance to much decay for twenty or thirty years is usually considered wonderful and perfectly satisfactory.
Notwithstanding the general injury to the appearance of the rotten stone, and the enormous losses annually involved in the extensive repairs, painting, or demolition, little concern is yet manifested by either architects, builders, or house owners. Hardly any department of technical science is so much neglected as that which embraces the study of the nature of stone, and all the varied resources of lithology in chemical, microscopical, and physical methods of investigation, wonderfully developed within the last quarter century, have never yet been properly applied to the selection and protection of stone, as used for building purposes. Much alarm has been caused abroad in the rapid decay and fast approaching ruin of the most important monuments, cathedrals, and public buildings, but in many instances the means have been found for their artificial protection,e. g., the Louvre, and many palaces in and near Paris, France, St. Charles Church in Vienna, Austria, the Houses of Parliament, etc., in London, England, etc.
In New York, the Commissioners of the Croton Aqueduct Department complained, twenty years ago, of the crumbling away of varieties of the gneiss used in embankments; the marbles of Italy, Vermont, and of Westchester county soon become discolored, are now all more or less pitted or softened upon the surface (e. g., the U. S. Treasury), and are not likely to last a century in satisfactory condition (e. g., the U. S. Hotel); the coarser brown sandstones are exfoliating in the most offensive way throughout all of our older streets and in many of the newer (e. g., the old City Hall); the few limestones yet brought into use are beginning to lose their dressed surfaces and to be traversed by cracks (e. g., the Lenox Library); and even the granytes, within a half century, show both discoloration, pitting (e. g., the Custom House), or exfoliation (e. g., the Tombs). To meet and properly cope with this destructive action, requires, first, a clear recognition of the hostile external agencies concerned in the process. These belong to three classes: chemical, physical, and organic.
The chemical agencies discussed were the following: sulphurous and sulphuric acids, discharged in vast quantities into the air of the city, by the combustion of coal and gas, the decomposition of street refuse and sewer gas, etc.; carbonic, nitric, and hydrochloric acids; carbolic, hippuric, and many other organic acids derived from smoke, street dust, sewer vapors, etc.; oxygen and ozone, ammonia, and sea salt.
The mechanical and physical agencies discussed were the following: frost; extreme variations in temperature, amounting in our climate to 120° F. in a year, and even 70° in a single day; wind and rain, most efficient on fronts facing the north, northeast, and east; crystallization by efflorescence; pressure of superincumbent masonry; friction; and fire.
The organic agencies consist of vegetable growths, mostly confervæ, etc., within the city, and lichens and mosses without, and of boring mollusks, sponges, etc.
The internal elements of durability in a stone depend, first, upon the chemical composition of its constituent minerals and of their cement. This involves a consideration of their solubility in atmospheric waters,e. g., the calcium-carbonate of a marble or limestone, the ferric oxide of certain sandstones, etc.; their tendency to oxidation, hydration, and decomposition,e. g., of the sulphides (especially marcasite) in a roofing slate or marble, the biotite and ferruginous orthoclase in a granyte or sandstone, etc.; the inclosure of fluids and moisture,e. g., as "quarry-sap," in chemical combination, as hydrated silicates (chlorite, kaolin, etc.), and iron oxides, and as fluid cavities locked up in quartz, etc.
The durability of a stone depends again upon its physical structure, in regard to which the following points were discussed: the size, form, and position of its constituent minerals;e. g., an excess of mica plates in parallel position may serve as an element of weakness; the porosity of the rock permitting the percolation of water through its interstices, especially important in the case of the soft freestones, and leading to varieties of discoloration upon the light-colored stones, which were described in detail; the hardness and toughness, particularly in relation to use for pavements, sidewalks, and stoops; the crystalline structure, which, if well-developed, increases the strength of its resistance; the tension of the grains, which appears to explain especially the disruption of many crystalline marbles; the contiguity of the grains and the proportion of cement in their interstices; and the homogeneity of the rock.
Again, the durability of a rock may depend upon the character of its surface, whether polished, smoothly dressed, or rough hewn, since upon this circumstance may rest the rapidity with which atmospheric waters are shed, or with which the deposition of soot, street dust, etc., may be favored; also upon the inclination and position of the surface, as affecting the retention of rainwater and moisture, exposure to northeast gales and to burning sun, etc.
In such methods, two classes may be distinguished, the natural and the artificial.
The former embrace, first, the examination of quarry outcrops, where the exposure of the surface of the rock during ages may give some indication of its power of resistance to decomposition,e. g., the dolomitic marbles of New York and Westchester counties, some of which present a surface crumbling into sand; and, secondly, the examination of old masonry. Few old buildings have survived the changes in our restless city, but many observations were presented in regard to the condition of many materials, usually after an exposure of less than half a century.
Another source of information, in this regard, was found in the study of the stones erected in our oldest cemeteries,e. g., that of Trinity Church. There could hardly be devised a superior method for thoroughly testing by natural means the durability of the stone than by its erection in this way, with partial insertion in the moist earth, complete exposure to the winds, rain, and sun on every side, its bedding lamination standing on edge, and several of its surfaces smoothed and polished and sharply incised with dates, inscriptions, and carvings, by which to detect and to measure the character and extent of its decay. In Trinity Churchyard, the stones are vertical, and stand facing the east. The most common material is a red sandstone, probably from Little Falls, N. J., whose erection dates back as far as 1681, and which remains, in most cases, in very fair condition. Its dark color, however, has led to a frequent tendency to splitting on the western side of the slabs,i. e., that which faces the afternoon sun. Other materials studied consisted of bluestone, probably from the Catskills, black slate, gray slate, green hydromicaceous schist, and white oolitic limestone, all in good condition, and white marble, in a decided state of decay.
The artificial methods of trial of stone, now occasionally in vogue, whenever some extraordinary pressure is brought upon architects to pay a little attention to the durability of the material they propose to employ, are, from their obsolete antiquity, imperfection, or absolute inaccuracy, unworthy of the age and of so honorable a profession. They usually consist of trials of solubility in acids, of absorptive power for water, of resistance to frost, tested by the efflorescence of sodium-sulphate, and of resistance to crushing. The latter may have the remotest relationship to the elements of durability in many rocks, and yet is one on which much reliance of the architectural world is now placed. Sooner or later a wide departure will take place from these incomplete and antique methods, in the light of modern discovery.
Reference was made to certain experiments by Professor J. C. Draper on the brownstone and Nova Scotia stone used in this city, by Dr. Page, on a series of the building stones, and by Professors J. Henry and W. R. Johnson on American marbles, in some cases with conflicting results, which were probably due to the limited number and methods of the experiments.
We have here to consider certain natural principles of construction, and then the methods for the artificial preservation of the stone used in buildings. Under the first head, there are four divisions.
Selection of Stone.—As it is universally agreed that the utmost importance rests upon the original selection of the building material, it is here that all the resources of lithological science should be called in. Only one investigation, aiming at thorough work, has ever been carried through, that of the Royal Commission appointed for the selection of stone for the Houses of Parliament. But the efforts of these able men were restricted by the little progress made at that time in the general study of rocks, and were afterward completely thwarted by the discharge of the committee and by the delivery of the execution of the work of selection to incompetent hands. There will be hereafter, from investigations made in the light of modern researches, no excuse for such annoying results and enormous expenses as those which attended the endless repairs which have been required, since a period of four or five years after the completion of the great building referred to.
Seasoning.—The recommendations of Vitruvius 2,000 years ago have been observed at times down to the day of Sir Christopher Wren, who would not accept the stone which he proposed to use in the erection of St. Paul's Cathedral, in London, until it had laid for three years, seasoning upon the seashore. Since then little or no attention appears to have been paid to this important requirement by modern architects, in the heedless haste of the energy of the times. Building stone, even for many notable edifices, is hurried from the quarries into its position in masonry, long before the "quarry-sap" has been permitted, by its evaporation to produce solid cementation in the interstices of the stone.
Position.—The danger of setting up any laminated material on edge, rather than on its natural bedding-plane, has been widely acknowledged; yet it is of the rarest occurrence, in New York city, to observe any attention paid to this rule, except where, from the small size or square form of the blocks of stone employed, it has been really cheapest and most convenient to pile them up on their flat sides.
Form of Projections.—The principle is maintained by all the best English and French architects that projections (i. e., cornices, sills, lintels, etc.) should be "throated," that is, undercut in such a way as to throw off the dripping of rainwater, etc., from the front of the building, but in New York this principle is almost universally neglected. It was pointed out that the severity of our climate even requires the further care that the upper surface of projections should be so cut as to prevent the lodgment or long retention of deposits either of rainwater or snow. It is immediately above and below such deposits that the ashlar of our fronts is most rapidly corroded and exfoliated, an effect evidently due mainly to the repeated thawing and solution, freezing and disintegration, which are caused by the water, slush, and snow, which rest, often for weeks, upon a window-sill,balcony, cornice, etc. Thus from the initial and inexcusable carelessness in the construction and form of the projections, and, later, the neglect of the houseowner, due to ignorance of the results involved, to remove the deposits of snow, etc., as fast as they accumulate on the projections, is derived a large part of the discoloration of the marble, Nova Scotia stone, or light colored granyte, and especially the exfoliation of the brownstone beneath the window-sills, balconies, etc., by the water alternately trickling down the front and freezing, by day and by night, for long periods.
The artificial means of preservation are of two classes, organic and inorganic. The former depend on the application of some organic substance in a coating or in the injection of fatty matters; but, as the substances are with greater or less rapidity oxidized, dissolved, and carried away by the atmospheric fluids, the methods founded on their use have been properly denounced by many authorities as only costly palliatives, needing frequent repetition, and therefore exerting an influence toward the destruction of delicate carving. The following were discussed: coal-tar; paint, which has been used in New York for many residences, as in Washington for the Capitol, and in London for Buckingham Palace, etc., but lasts only a few years, and often even permits the disintegration to progress beneath it; oil, often used in New York, but as objectionable as paint; soap and alum-solution; and paraffine, beeswax, resin, tallow, etc., dissolved in naphtha, turpentine, camphene, oil, etc.
The preparations of an inorganic nature, which have been proposed and used abroad, have in some cases met with success; but the exact nature of their action, and the conditions to which they are each suited, are yet to be investigated, especially with reference to the entirely different climate by which the stone in our city is being tried. The processes which have been proposed, and in some cases practically used, involve the application of the following substances: waterglass, in connection with salts of calcium or barium, or bitumen; oxalate of aluminum; barium solution, in connection with calcium superphosphate or ferro-silicic acid; copper salts, used by Dr. Robert in Paris to stop the growth of vegetation on stone, etc. There is certainly a call for processes by which, at least, those stones which are used in isolated, exposed, and unnatural positions may receive artificial protection, such as the stone sills and lintels of windows, stone balusters, projecting cornices, and ashlar-stone set up on edge. It will doubtless be found that only those stones which possess a coarse, porous texture and strong absorptive power for liquids will be found particularly available for protection by artificial preservatives, and that such stones should indeed never be used in construction in a raw or crude state. In the spongy brown and light olive free-stones, a marble full of minute crevices, and a cellular fossiliferous limestone, a petrifying liquid may permeate to some depth, close up the pores by its deposits, and incase the stone in solid armor; while, upon a more compact rock, such as a granyte or solid limestone, it can only deposit a shelly crust or enamel, which time may soon peel off. The carelessness with which stone is selected and used, and the ignorance in regard to its proper preservation, when the decay of a poor stone becomes apparent, have led to an increased use of brick and terra cotta, much to be deplored; durable stones are to be obtained in great variety, methods for the preservation of the porous stones can easily be devised, and stones of a fireproof character do exist in this country in abundance.
In conclusion, three suggestions were offered: 1st, that householders invoke the magic use of the broom on the fronts of their residences as carefully as upon the sidewalks; 2d, that house-builders insist upon the undercutting of all projections, and the exclusion of brackets or other supports to sills and cornices, which only lead to the oozing of water and a line of corrosion down the ashlar; 3d, that house repairers recut the projections in this way, whenever possible, and entirely avoid the use of paint, oil, or other organic preservatives.
"Elephants," says Mrs. A. H. Brackenbury, of Singapore, to whom we are indebted for our sketch, "work in the timber yards of Moulmein, carrying huge planks, sometimes two or three together, and with great care and exactitude piling them in stacks one over another. The old hands take a sidelong view with one eye closed to test the perpendicularity of the stacks. The elephants lift the planks with their proboscis on their tusks, and then tuck their trunks around the burden, and march majestically off as if they were carrying nothing. A man sits on each elephant's neck to direct him, which he does by kicking or pressing behind their ears.
"In Africa the elephants are being so persistently slaughtered for the sake of their ivory that they are likely soon to become extinct.
"Would it be possible to breed them on farms as ostriches are bred, and then to employ them in navvy work, for which they are probably as well suited (education being supplied) as their Asiatic cousins?
"Moulmein is a very pretty place, and its charms are enhanced by its being out of the beaten track of tourists. It is up a river, and there are many islands on which are perched the daintiest little gilt and painted Burmese pagodas. The scene recalls the well known view on the willow-pattern plate of our childhood, which plate has once more become fashionable."—London Graphic.