^ establishment; whereas to the consumer of steam, the perfect certainty of the amount and regularity of the supply of power is a great auxiliary in conducting business. For a steam-engine, the only use of water is a sufficiency for the boiler; and in these days of economy of heat and steam, a very small quantity of fuel is used, and but little water. We have seen a rotary-engine, estimated at 15-horse power, evaporating but 40 gallons per hour. 6th. Delay in winter, and in our uncertain climate this may sometimes be considerable, and, in an establishment of great extent, perhaps fatal. To balance all these expenses, peculiar to the use of hydraulic power, there is, as far as we can recollect, but one peculiar to that of steam, namely, fuel. Now, in saw-mills this expense is nothing, and in all instances much less than formerly. Our persevering countryman, Dr. Nott, has already succeeded in greatly reducing this item of cost-and he does not yet appear to be satisfied. As regards fuel, Avery's engine has immense advantages over others, inasmuch as the quantity of water used is less than in any other case. The elasticity of the steam operates more advantageously than in any other construction, the small quantity of water used being a proof of this. In the engine above referred to, the cost for coal was rather less than one dollar for ten hours. It is almost needless to observe that, in many large establishments, manufactories, &c., the application of a portion of the steam to heating, &c., nearly, if not quite, compensates the cost of fuel. The certainty and uniformity of this method of drying goods have fully established its superiority. Indeed, in the art of dyeing, certain colours owe their brilliancy to the rapid and high heat of steam, and they could be produced in no other way. While speaking of this use of steam, we must notice an engine erected in the Astor Hotel. This is a small engine of 5-horse power; its use is to pump water from the different cisterns to all parts of the house-supply the baths with hot and cold water-clean knives-brush shoesroast and grind coffee; and the steam cooks the various dishes in the kitchen, and also dries the clothes, which by this method of proceeding are ready for use with unprece dented dispatch. To these and numberless other uses is this engine turned, saving an immense number of servants, a great quantity of fuel, and a vast deal of time. (The exhaust steam-pipe of this engine is over 300 feet long.) One of the greatest advantages of steampower, in many cases, is, that it admits of change of locality, without injury to the machinery, and often with benefit to the employer. In this respect, again, Avery's engine stands pre-eminent. The machinery is beautifully compact, and consequently portable. An engine of 15-horse power is hardly a load for a horse, the whole weighing less than 600lbs. Let us suppose, that a man purchases a piece of timber land, of prime quality, but, unfortunately (as is thought), away from any water-course. Let him procure an Avery's engine; and this, connected with his saw-mill, can be placed upon wheels and moved, by the engine itself, if he pleases, to any part of his land. (Mills capable of such an arrangement, and very compact, are now easily to be procured.) Let him locate his mill near a spring, and commence operations. The waste and rubbish, that in most cases is a drug, is entirely consumed by the engine; the ground is cleared, and nothing is to be removed but the perfectly formed timber. Among other useful applications of such an engine, in the forest itself, no one can be equal in beauty of operation to the valuable stave-machine of Philip Cornell, N. Y. This machine promises to be of great service. With such an arrangement as that of the saw-mill above-mentioned, nearly, if not quite, double the usual number of staves can be cut from the timber before transportation, and these are already dressed and ready for use, either for liquids or solids. These are only a few of the very many useful applications of this sort of travelling machines. Others will suggest themselves to our readers. It must be very evident that, whatever brings into use property of little or no value, enabling the produce of such land to compete successfully with that of much better, must add to the wealth of the landholder, or timber-merchant, a sum equal to the cost of the best land. Thus a great uniformity of value would result, and of consequence a more equal competency to those on, or away from, great water-courses and canals. WORK DONE BY THE TEN BEST ENGINES OF THE LIVERPOOL AND MANCHESTER RAILWAY, DURING THE YEARS 1831, 1832, 1833, AND THE TWELVE FIRST WEEKS OF 1834. (From Pambour on Locomotion.) This statement shows what can be expected from locomotive-engines, when constructed with care and of good materials; and there is no doubt that, in time, more work will still be obtained from them. MARBLE CEMENT. Total Time the Engine has been on the Road, either in Activity or in Repair. Miles. Weeks, 23,212 52 22,528 44 20,404 52 Among those engines, the Liver had worked for 107 weeks, had travelled 52,865 miles, or, on an average 494 miles a week during all that time; the Firefly had worked 57 weeks, had travelled a distance 33,421 miles, or 586 miles per week, and neither of these engines at the period in question, had yet required a fundamental repair.* MARBLE CEMENT. An important improvement, which has been for several years in progress, is about being introduced to the more general notice of the public, and we believe into extensive use for building purposes. It is a composition or cement, of which the principal ingredient is marble or lime stone, which, when applied to the inner or outer walls of buildings, presents the appearance of polished marble, of the various hues and qualities which distinguish the beautiful material imitated. What would be thought of a magician who possessed the power of changing the sombre brick and stone walls of the buildings of a city, in one week, into substances resembling the most beautiful Grecian, Italian, Egyptian, or Verd Antique marble, or porphyry, like the rock of Gibraltar! Yet all this may be done by this invention of a humble citizen, of Orange county, in this State. This cement has been sufficiently tested by experiments on buildings, to satisfy practical men of its decided superiority over any other cement," stucco, or other hard finish for walls, hitherto known. In our next Number we expect to be able to furnish the publie with some interesting particulars on this subject; and in the mean time we can state, that a Company has been formed in this city to carry on the operations connected with the manufacture of this new cement, and its application to buildings.-New York Railroad Journal. The first column in the above table is the same as given in the Memoirs of the Astronomical Society, vol. ii. p. 516, and in the Edinburgh Journal, No. XI. The next, or middle, column is the th part of that preceding. The last column is from Professor Struve's new results, as stated in the above Journal, which are nothing more than a reduction of his first observations, as the 17th part of the first column is the precise difference between the first and the second observations of Professor Struve, with the exception of the fourth satellite only of Jupiter, which, it appears, the professor forgot to correct! Now, had the professor's micrometer, in the first instance, given the diameters too large, why not. state that a reduction was necessary, and that the latter measures were the results of such reduction, instead of assuming that they were obtained from a more nu merous set of observations than in the first instance? As it is millions of times more probable, that if fifteen dice were thrown out of a box that they should all of them come up aces, than that the above results should obtain from observation only!! Now, Dr. Herschel was in possession of a telescope of a magnifying power ten times superior to that of Fraunhoffer's; it is therefore very unlikely that Dr. Herschel should have been in error oneseventh part of the whole, if observations can be made in England with any thing like the precision attained to by Professor Struve, as there is a difference resulting from the measurements of the two observers in the exterior diameter of Saturn's ring of 28,500 miles. I am, Sir, yours, &c., J. UTTING, C.E. Lynn Regis, July 22, 1836. SIDERIAL TIME. Sir,-Your scientific correspondent, Mr. T. G. Waldron, thinks (see No. 674) that the longitude of a ship at sea might be correctly found by means of a chronometer made to keep siderial time, and adjusted to some port whose longitude is exactly known; of course, Greenwich is the place best suited for that purpose, as all the articles in the Nautical Almanac are computed for Greenwich time. Mr. Waldron states, that by observing the exact time that any fixed star passes the meridian, by a siderial chronometer set for Greenwich time, the longitude of the ship may be determined. This is no doubt all true, provided you know that your chronometer is right for Greenwich time, or that the quantity of its daily gain or loss of time has been previously established; and also that you can determine by an observation, or a set of observations, the exact time by your chronometer (or within a small fraction of a minute) when the star transits the meridian. Before proceeding further I would remark, is there any thing particular in a siderial chronometer that gives it a preference over that of a chronometer that keeps mean solar time (the principle upon which all marine chronometers are constructed)? I certainly answer none whatever, or rather the advantage for the navigator would be in favour of a chro nometer set for mean solar time. A siderial and a mean solar day are both constant portions of time;* a siderial revolution of 24 hours is exactly equal to 23h. 56m. 4·0906s. of mean solar time; and 24 hours of mean solar time is equa to 24h. 3m. 56′5554s. of siderial time. In order that we may judge of the merits of both methods for determining the longitude at sea, suppose that on March 31, 1836, a ship at sea found hy an observation that the star Regulus passed the meridian at 11h. 10m. 20s. p. m. by a siderial chronometer regulated for Greenwich time, then to determine the longitude of the ship : H. M. S. Regulus passes the meridian of Greenwich, 9 59 39 siderial time. March 31, 1836, at. Hence (1 10 29.5) × 15=17° 37′ 15′′ W. longitude. Now, a chronometer which indicates on March 31, 1836, 11h. 10m. 20s. of Greenwich siderial time, would be expressed by a mean solar chronometer at the same instant, and also set per Greenwich time by Difference of meridian in mean solar time.. The difference of the meridians by both methods being exactly the sameand, of course, the longitude the same. But I am afraid that the longitude determined by the above method could not be altogether depended upon. The only method (as far as I am aware of) of determining the time at sea when any of the heavenly bodies pass the meridian, is by taking a number of altitudes before and after the star passes the meridian, carefully noting the corresponding times indicated by the chronometer; then the time opposite to the greater altitude will be that of the star's passing the meridian. But every one knows who has considered the subject, that for a small portion of time before and after any of the heavenly bodies come to the meridian, there is hardly any perceptible change in their altitudes; and that an error of 1 minute of time produces an error of 15 minutes of longitude; or if 4 minutes, the error would be a whole degree of longitude. Or if equal altitudes of the star were taken when a considerable way to the eastward and westward of the meridian, the middle time (if the ship was lying to, or making little or no way during the time of taking the altitudes) would indicate (as there is no change of declination) the time the star passed the * The difference between apparent siderial time and mean siderial time amounts only to 23 seconds in 19 years. (Communicated by the Inventor.) The encrustation of the boilers of marine-engines has been long acknowledged one of the greatest drawbacks to the application of steam to navigation; and the many evils arising from it-particularly in sea-going vessels-are too familiar to every practical engineer to require explanation. The great loss of power from blowing out the boilers; the great waste in fuel to supply the place of so much hot water; the valuable space occupied by a larger quantity of coals than would otherwise be required; together with the rapid wear of the boilers themselves, even under the most careful management;are among the disadvantages with which steam-ships engaged in the coasting trade, or destined for foreign stations, have to contend. Economy of space and fuel, and the durability of the boilers, are objects of the first importance; and whatever will, in a simple and effectual manner, come in aid of these requisites (with out introducing other disadvantages), must be considered an important advance towards perfecting steam navigation. I am encouraged to think that I have devised a remedy for these evils, simple and cheap in its application, taking up no room, adding nothing to the tonnage of the vessel, and perfectly efficient in its operation. It appeared to me not a little singular, that so many attempts should be made to condense inside the vessel by means of unwieldy tanks, which, at the best, must be but imperfect coolers, when there is so simple and perfect a condenser outside as the open sea or river.. I con ceived that by cooling down the water in the hot well to the temperature of the external water, by means of a pipe, so placed outside the vessel as to receive the direct action of the water, in order that condensation might be effected by injecting, again and again, a portion of the same water, while the remainder is returned to the boiler, it would succeedmore especially as such a plan would involve no alteration in principle-in producing a most simple and perfect mode of preventing encrustation, applicable with the greatest facility to any vessel in a few days, and without making any alteration in the engine itself. By this method, the injection-water, after condensing the steam, is conveyed in the usual manner by the air-pump into the hot well, from whence a portion of it enters the refrigerating-pipe at about 96o; and by the rapidity with which the pipe is brought into contact with the constantly changing particles of water by the motion of the ship, every portion of warmth is speedily given out; and long before the water completes its passage, it will become of the same temperature as the external water, and thus be ready for injection again. The remaining portion of the water escapes to the boiler by means of a float in the hot well, which moves on friction-rollers, in front of the orifice leading to the feed-pump, and rises and falls freely with the rise and fall of the water in the hot well. It is evident that by this means the circulation of the water in the refrigerating-pipes will be kept up with the utmost regularity, as only the precise quantity that has been previously used for injection will again flow into the refrigerating-pipe, to supply the vacancy thus momentarily occasioned, for the purpose of again being injected; whilst the remaining portion of the condensed steam, which will be the exact quantity that has been evaporated, will elevate the float in the hot well until it has escaped to the feed-pump. Thus the same water will be used over and over again in the boiler, and encrustation effectually prevented; while, at the same time, the supply will be in exact proportion to the quantity evaporated, and, on account of the simplicity of the contrivances, without any risk of derangement in either case. The steam from the safety-valve will be condensed by leading it into the condenser or external pipe; and by ap |