18 ON ASPHALTUM, OR JEWS' PITCH, &c. of which may be combined in many ed by the Arabs for sale. The most different manners. These experi- abundant deposits of this substance ments teach us. at least, that when we can employ, in a convenient manner, many little cords, and can stretch them equally, these little cords would be in a state of producing a greater effect, or of resisting a greater effort, than a cable composed of all these small cords would be. Lastly, it we cannot decide what the strength of a cable is we may decide what are the limits of its strength, by seeking what the force of one of the small cords is which compose it, and by examining what is the number of these cords; since we have seen that the force of the cable is less than the sum of the forces of all these cords. Lond. Mec. Mag. ON ASPHALTUM, OR JEWS' PITCH. Asphaltum is a brittle blackish substance, having a smooth, conchoidal fracture; it melts when heated, and readily burns, giving out a dense, black smoke. The Egyptians employed it in embalming their dead, and the sear-cloths of mummies, made with this substance, remain perfectly unaltered to this day. Strabo and Diodorus mention this substance; the former, lib. xvi, gives an accurate description of its properties, and, in particular, refers its evolution from the earth to the action of subterraneous fire; he quotes Eratosthenes for its use, as an ingredient of the mortar with which the walls of Babylon were built. Piny makes mention of its similar application, lib. xxv. He enumerates the places where it is produced, and after describing its medicinal virtues. he states that it is farther employed for painting or colouring statues. The ancients were well aware of its near relation to naphtha, and recount some strange stories dependant upon its highly combustible nature. At present it enters into varnishes, being soluble in some oils, and eminently so in rectified petroleum or na htha. Asphaltum is found in Switzerland; and at Aolonia, in Albania. It is abundant on the surface and on the shores of the Dead Sea in Judea, where these lumps are collect are in the islands of Barbadoes and Trinidad; in the former it is found as a highly bituminous earth, but being in a state of great impurity, is only used as coal for fuel. In the latter island is a complete lake of this substance. On one side of the island a cape, or headland, projects consideraby into the sea, and upon this cape, at an elevation of 80 or 100 feet above the level of the sea, the tar lake, as it is called by the English, is situated. Its strong and disagreeable smoke is perceptible at a considerable distance out at sea; and on a nearer approach the surface appears smooth as a mirror. The circumference of the lake is a circuit of about three miles, its depth is unknown; but in hot weather the surface becomes softened to the depth of an inch, so as to preclude the postimes it is covered with innumerable At other sibility of walking upon it fissures, which are continually c sing in one part and reopening in soure the whole mass is floating. Thes other, so as to render it probable that fissures are eight or ten feet deep, and contain clear water, abounding with small fish. IRON MASTS. Mr. Vauquelin was therefore desired to examine these spots chemically, to determine their nature. For this purpose he scraped off from the sabre some of the red matter, and put it into a small glass tube closed at one end, and stopped the other with a strip of litmus paper, which had been previously turned red by an acid. The tube and red powder were then heated by a lamp, a yellow steam was produced, which restored the reddened paper to its original blue. The same experiment was made with the powder scraped from the knife, and the same effects were produced As this alteration of the colour showed the presence of volatile alkali in the red spots, and this alkali is well known to be present in all animal matters, the suspicions previous ly raised were considerably strengthened; but Mr. Vauquelin was not thoroughly satisfied. The experiment was therefore made with rust scraped from a piece of iron found by accident in the judge's closet, which gave the same result as the other rust; and thus destroyed the suspicions that the unguarded assertion of the medical man had occasioned. These experiments prove that when rust is formed in houses, it is capable of absorbing and even retaining the volatile alkaline vapours usually floating in the air in inhabited rooms. Rust also appears to absorb animal vapours, for in the experiments some traces of a brown oil were observed on the surface of the glass tube. Mr. Laugier has examined some 'rust found in his own laboratory, and not only confirmed the observati ns of Mr. Vauquelin, but also detected the presence of sulphuric acid in the rust. Lond. Mec. Jour. IRON MASTS. SIR,-At a period when Science is making such rapid strides, and its ele ments so generally diffused, even among the labouring classes, it cannot be matter of surprise that the public ttention should be alive to any im 19 provements in the form of our ships of war to the conveniences afforded for their skilful navigation, or to any other circumstances which may place us higher in the scale of improvement than any other naval power. The columns of our newspapers have been much occupied of late with accounts of the trials of the three experimental sloops of war, Champion, Pylades, and Orestes, and a deep interest has been excited as to the final result of those experiments; but this interest rests chiefly in the minds of those who are little able to judge of the value of the experiments in a Pailosophical point of view. In the absence of data as to the relative sizes of the vessels, the area and form of their fore and after bodies, form of their midship sections, the their draught of water, the dimensions of their masts and yards, and area of their sails, no definite judgment can be formed of the merits of their constructors; for let it be recollected that the man who can build that ship which shall have a maximum of good qualities with a minimum of defective ones, under all circumstances of sailing, and in all states of the weather, and can do this so as to carry the required number of guns, in a ship of the least possible dimensions (to secure good qualities,) is to be considered, not only in an economical point of view, but in a scientific one, as the most skilful constructor. It is a well known fact, that a person totally ignorant of the science of naval architecture can build, with success, a large ship to carry only those guns, and that quantity of stores, usually put on board a small one, and she shall have better sailing qualities than the smaller vessel, although the former shall be far inferior to the latter in scientific construction. But, Sir, I look with a deeper interest to the result of the next cruise, than the quicker or less quick passage of these three sloops through the water, when I turn my eyes to the experiment which is being tried in the Phaeton frigate which accompanies them. This ship, it appears, has a main-mast and bowsprit of iron, made under the patent-right of Mr. Robert 20 HINT TO BRE WERS, &C. Bill. If this plan should succeed, it will confer a benefit on the English nation of no mean importance; it will make us at all times independent of foreign countries for a supply of mast timber-it will give energy to British industry, and employ a large capital at home-it will decrease very considerably the expenses in the equipment of a navy; and, what is of still more importance, by the powerful ventilation which they afford, the health and comfort of the seamen will be promoted, and the durability of the ship ensured. situated, would draw the weight res quired with the same ease as thr horses in the ordinary way, which will be the means of saving one horse per dray, and prevent their block ng p the streets, as they now do, when veral are following one another Lond. Mec. Mug. MARQUIS OF WORCESTER'S NINETY. We are unable to answer the the me By a new and happy improvement in this species of mast making, and for which the inventor has lately taken out an additional patent, masts can be made of the required strength, and still preserve a comparative degree of lightness; and farther, iron masts may be taken out to foreign stations in small parts, built on board ship by the mechanical means which every ship affords, and thus render a masting machine unnecessary. By this, in time of war in particular, a very modification, of his steam engine; great saving will arise. Added to all these advantages, an iron mast, even according to the present high price of the raw material. can be made at half the cost of one of wood, and will, most probably, last ten times as long. Your obedient servant, HINT TO BREWERS. SIR-I much wish through the medium of your valuable work, to recommend that the brewers in this great town try the effect of double shafts, so as to accommodate two horses abreast, as I think there is little doubt but that two horses, thus this at least is more charitate than to set him down for a false pretender, which we should be constrained to do, could we believe that he designed to impress the opinion that be had effected it by any comb Son of the mechanical powers whate ver-AM. ED. NOTICE Distant subscribers to the Ameri Communications for the American Mechanics' Magazine. William Van Norden, Printer. AMERICAN MECHANICS' MAGAZINE, Museum, Register, Journal, and Gazette VOL. II.-No. 28.] SATURDAY, AUGUST 13, 1825. [ $4 PER ANNUM. 22 INLAND BOAT NAVIGATOR, BY STEAM. DOUBLE INCLINED PLANE, AND INLAND quaintance with the subject; where BOAT NAVIGATOR, BY STEAM. Fig. 2. this does not exist, we find men plodding successively in the same way, without the thought of variation or increased advantage; but in the reverse, which we rejoice to see becoming fashionable, they substantiate their claim to intelligent beings, by conforming their works to rational principles. We have been led to these remarks from a knowledge of the means that ble intercourse than at present exists, are now taking to open a more feasibetween the vallies of the Susquehanna and Ohio rivers. This project connected with the prosperity and political happiness of our country is of very great importance, and no doubt will be very speedily carried A transverse sectional view of the en- into effect, either by the construction gine house, boat, &c. SIR, AS plans of improvement are projected, no matter what their magnitude or how bold their character, so their execution come within the limits of human ability, the means of carrying them into effect seem to be presented. It is true, some of them do not deserve consideration; others again possess different claims to merit and not unfrequently the less meritorious, presented under more imposing circumstances, obtain precedence in the public estimation, to the injury of the community and of the individuals more immediately concerned. When errors have been once adopted, prejudice and interest tend to continue their currency as truths; and ages, in some instances, pass away before they give place to more correct notions or practice. Many cases to the point could be given in support of this position; but our business is not with the past, it relates to the future; and we would recommend to those to whom the choice of plans may be delegated, as a means of correcting the evil, not to adhere too tenaciously to antiquated systems; for human wisdom is progressive, and to say that any thing of human devising is perfect, is an acknowledgment of our ignorance or indolence. To be able to devise or adopt with judgment, implies a thorough ac of railways or a canal. The former, if well built, cannot fail to answer the most valuable purpose; because it will allow of constant use at all seasons of the year; while the latter can only be used between the departure and accession of the frost. Besides, some doubt exists in respect to obtaining a supply of water on the summit level of the Allegany ridge, or even at a lower level, contemplated to be secured by tunnelling. To obviate these difficulties, Archibald Tanner, Esq., who resides in the neighbourhood of the proposed canal site, suggests a combination of these two modes of intercourse; that is, to canal from these rivers toward the mountains as near as may be feund practicable, and then construct two sets of inclined planes, the one somewhat elevated above the other, to constitute a continuous route. On the lower plane he proposes to run a carriage, or cradle, calculated to receive a loaded boat, and on the upper plane, a carriage supporting a steam engine of sufficient power to propel itself and one or more of these cradles and boats, as occosion may require. Mr. Tanner does not, however, confine his views of the application of his plan to this situation alone; he thinks it may be advantageously applied in all similar situations, viz. where the distance is considerable, and water cannot be readily obtained to feed locks and |