The Oldest Circular Saw. MESSES. EDITOES :—I noticed in your valuable paper of September 41th an article entitled, —First Circular Saw,” by Lemuel Read. I have a circular saw in my possession which I obtained in the year 1837, and have kept it on account of its antiquity, as I was informed that it was the first circular saw ever forged in America. It was made in the year 1793 by Benjamin Bruce, of New Lebanon, N. Y. It is 13J inches in diameter, and very different from saws in use at the present time, having an eye in the center If inch square and six slots in the plate to keep the saw from heating when at work, thus the teeth are throe to one inch, and filed about the same angle as a common hand saw. I am informed by an aged person, now living, that he came here in the year 1800, and there was at that time a circular saw in use for edging boards and sawing rims for spinning wheels, and had been in operation 3 or 4 years. The ideaof acircular sawfor cutting boards was taken from a small saw first made of tin and used in a turning latlie by Amos Jewett, of New Lebanon, N. Y., a clock-maker ; and he made use of it in cutting the teeth of wheels, which were V-shaped, for his clocks. I have conversed with him in my younger days upon the subject, but never ascertained the time to date his first experiment with circular saws. We have a large building standing in our village of which the covering and floors were edged and matched with circular saws in the year 1815 or 1816. So I think friend Read is not at the top in antiquity. GEO. M. WICKBRSHAM. Shaker Village, New Lebanon, N. Y. [We remember to have seen and examined the Bruce saw a few years ago, when visiting the Shakers at New ebanon. Friend Wickersham then called our attention to it as being probably the oldest circular saw in the coxmtry. It any of our readers can refer to one of earlier date we hope they will write us the particulars.—EDS. Curious Antique Astronomical "Watch. MESSRS EDITORS :—The very interesting account in your paper of 31st August of the great astronomical clock of the Beauvais Cathedral, and also of the Strasbourg Cathedral clock, reminds me of an astronomical watch that I often delight to look at which is no less remarkable in its way. A short review of its performances may interest your thousanus of readers, as it is a curiosity of science and mechanism. It is not one of those mere mechanical toys contrived to amuse the monarchs and other grown-up children of luxury of a century or two back, which, besides keeping incorrect time, when running at all, could be made (by touching certain springs or otherwise) to strike a bell or play a few bars of music, or display soldiers moving past a window in its face. On the contrary, this elegant watch, made in the highest finish and good taste, and without a tawdry ornament is a perfectly reliable time-piece. It performs all its movements with the most accurate punctuality, showing the exact time of day, the hour, minute, and second, the month, the day of the month and of the week, the age of the moon, the moon's phases, the zodiacal and planetary phenomena of the present time, etc. In outward appearance, it is a plain gold watch, with two enameled faces protected by crystals. Each face, with its own features, will be described separately. Its size is two and three eighths inches in diameter and about five eighths of an inch in thickness. The principal face exhibits three dials, two smaller ones occupying opposite positions in the upper and lower halves of the greater dial. Aljove this face on the rim of*the case, is the legend, in Roman capitals, " INCHRTA EST IIORA, AETERNA RESPICB," which may he rendered. The hour is uncertain—look at things eternal. The outside edge of this face contains a circle divided into seconds, and traversed by an independent secondhand once in every minute ; while balanced on tlie same central point is another similar delicate hand wliicli makes its circuit only once in two years ! one end pointing to the months, the other to the twelve signs of the zodiac correspoiding with each month in the year. The figures representing these signs are most exquisitely done in miniature, in black on the fine white enamel face, as is also the lettering of the names, in French, of the months. The divisions and subdivisions of this and every other dial are spaced with geometrical precision, and the works perform their part so accurately that the xoint of each one of the twelve hands of this watch arrives at the proper instant exactly on or over its marked position, a proof of the superiority of the workmanship. The upper small dial on this face has three hands pointing severally to the day of the montli and the days of the week, in French, and their corresponding celestial bodies in the fol lowing order : The sun, the moon ; the planets Mars, Mercury, Jupiter, Venus, and Saturn. The lower small dial on this face shows the hours and minutes in the usual manner of watches. Below this face, on the rim of the case, is the inscription, Tempus renmi imperator—" Time, the ruler of all things." The opposite face of this superb watch presents the same general arrangement of three dials, but the larger dial is RISO divided into equal it))pcr iind. lower parts, the latter enameled in black to represent night, with the moon, stars, etc. This dial is figured differently from modern dials, having 24 hours, 12 for the day and 18 for the night, -with the subdivisions and hour and minute hands accordingly. On the case around the lower and dark half of this dial is the inscription. Sapiens insipientibus sicut luna in mote—" The wise man to the ignorant is as the moon to the night." On the case around the upper half of the dial is engraved, in Italian, iVii vi son tendire per M creo la luce—"There is no darkness for Him who created the light." In the dark half of this dial is a smaller dial with hands showing the age of the moon, the moon's )hases, and the day of the lunar month. The small dial in the upper half of this face has an index gage and pointing hand for regulatiiig the grand movement, which controls tke entire twelve hands and movements. Being also wound up as well as regulated from the outside, the works within are permanently closed from dust as well as excluded from prying and meddlesome curiosity, to which precaution we attribute its present perfect condition, being more than two hundred years old. The durability of watches when well made is very remarkable. This valuable, complicated, and beautiful piece of mechanism is in perfect running order, and ppjforms with astonishing precision in all its movements. It is a French watch, made by Robert et Courvoisier. It musthave occupied many months, perhaps years, of time and labor in its construction, and though it is small and handy enough to be carried in the rich man's pocket, it is well worthy a high place in the cabinet of the gems of science and art. It is now the property of Mr. F. W. Chamberlain, 233 Hanover street, Boston. F. H. F. Steam and Hot-Water Pipes. MBSSBS. EDITOBS :—In an article on the causes of fires in manufacturing establishments from steam pipes, etc., in your paper of the 4th inst., I notice the terms steam and hot-water pipes, are so commingled that _ one would suppose that they were so nearly alike as to produce the, same results, the only real difference being a few degrees in temperature. In a steam heater a portion of the water (at least that in the pipes) is converted into steam before the fixture operates, while a hot-water heater, properly constructed, is simply a circulation of water, filling boiler and radiators, warmed, but never reaching so high a temperature as to form steam, and working with the same pressure that is sustained by the lead pipes of the plumbing fixtures in our houses, consequently no more liable to explosion, and limited to a temperature of 200 at the boiler there is about as much' danger of a plumbing job setting the house on fire as from a properly-constructed hot-water fixture. My impression is, that in all the cases where hot-water pipes have been reported as producing the effects described they ?verc in reality steam pipes. To save the giaterial requisite in the radiators for heating at a very low temperature is the inducement to use steam. If specifications for constructing hot-water heaters required that the requisite heat in the rooms warmed, say 70, should be xjroduced with not exceeding 200 at the boiler, there would be no such chemical action as Mr. Braid wood describes, or consequent danger from fire, not to mention the superior quality of heat obtained from surfaces at such low temperatures. A SUBSCEIBBE. Baltimore, Md. New Wall Covering. MESSES. EDITOBS :—In the concluding remarks of Mr. Wight's paper on " Fire-proof Construction " in your issue of tho 28th ult., the following remarks occur : " The stone slabs of Mr. Eidlitz are the only rigid material thus far used successfully with iron beams—they are doubtless the handsomest material that can be used for that purpose, but are open to the objection of being heavy and expensive"—it will be pertinent to our inquiry, therefore, to ask if there are any other rigid" materials adaptable to this purpose, and possessing the desired qualities of lightness and cheapness. Fur-ther on, he remarks that " the cheapest material for wall covering in natural materials would be slabs of white marble, which would cost f 1-50 per foot, and three coat plastering laid on iron lath f 1-34 per foot." I would inform Mr. ?Vight that there is in use by the architects of the Southwest, a composition called by the inventor Lithomailite, produced by a method of hardening and marbleizing plaster of Paris, and giving it a high and durable polish. This, I think, is the desideratum in fire-proof buildings, with the material advantage over marble slabs and plastering, that it does not cost over one seventh the price of either of the above styles of finish. It can be put on walls or ceihngs in ashlers to suit, at twenty cents per foot. An office 20x40—16 feet high, finished with marble slabs would cost for the walls alone $2,886, while both ceiling and walls could be finished in Lithomailite for $544. The imitations of precious marbles in it are inimitable. It is hard enough to shiver a door knob or key when slammed against it. It has the hearty indorsement of the leading architects of the South, and is the strongest and most elegant substitute for plastering that I have seen in a building dm-ing an experience of over thirty years. Gt. W. LINCOLN. Memphis, Tenn. Explanation of a Curious Phenomenon. MESSBS. EDITOBS :—You are herewith offered an explanation of your " Curious Phenomenon," published a few weeks ago. Subject : Jar cracked across the bottom. Jar leaks on hard, unpainted surface ; is tight on painted surface. ? painted surface is tenacious ; oil makes it more soi An unpainted surface is not tenacious ; oil makes it less so. The former holds the jar .together. The latter offered no resistance to the outward expansion of the bottom of the jar (causedby its own weight) and oonsequeiit opening of the crack. Z. Pittsburgh, Pa. A Night eun-Slght Wanted. MESSES. EDITOBS :—Could not some one invent a contrivance for illuminating the sights of guns and rifles at night, so as to enable to shoot with certainty when- dark ? Everyone knows what difficulty attends taking aim vpith.rifles when dark. Might it not be done by a small electric spark on each sight, produced by a miniature battery, concealed in the stock of the rifle or gun, and led to the proper place by a thin copper wire, covered with silk thread, a;nd which could be removed or put on at pleasure ? I leave this idea to some inventive genius, and I have no doubt, by producing some simple and easy-managed contrivance, a patentee might make a good thing for himself and earn the thanks of many a sportsman and frontiersman, if not a glorious place in history. FBONTIEB. New Mexico. Kallway Ties. MESSBS. EDITOBS :—In reading a recent answer to a correspondent in your paper, touching the life of oak railroad ties, stone ties, etc., a few practical thoughts, the result of 14 years' experience, suggested themselves. The lasting of oak ties depends very much upon' the manner of putting them down, and the condition of the wood at the time i-hey are laid. Take a red-oak tie from the stump with all tEe sap in and it will not last three years ; but if piled up and well, seasoned before laying, it will last six years. The same remarks will apply to white oak. There is ,often a great deal of carelessness on the part of the foreman of repairs in this particular. Speaking of stone ties, I think the day is not far distant when wrought iron stringers will be used, broad on the surface, so as not to sink under pressure, and bolted together. There would be sufficient spring on such ties, and the rails can be thoroughly fastened to them. They would not present the rigidity of stone blocks, or fail in durability. Belvidere, N. J. JACOB STONB. Testimony of an Advertiser. In a recent issue under the head of " Business Hints," we took occasion to speak of the value of the SciBNTlPiC AMEB-ICAN as an advertising medium. We are frequently receiving evidences of the correctness of our statement from advertising patrons, an example of which we present herewith : You are foUo'wing my wishes. You may continue to advertise until I notify to the contrary. I have found during the short time I have had the cupola notice in your paper it has called the attention of iron founders to my improvement, and increased my orders and sales more than all the circulars I have ever sent, and I am compelled to believe and free to admit that the SCIENTIFIC AMERICAN is the best paper for me-chanicsto advertise in I know of. AJSIBL PEVT. Lowell, Mass.