NOTES ON SCIENCE MECHANICAL INVENTIONS ETC.

New Zealand Herald, Volume XXIX, Issue 8842, 2 April 1892, Page 4 (Supplement)

NOTES ON SCIENCE MECHANICAL INVENTIONS ETC.

AN ACCURATE SCREW. A method of forming a very accurate screw lias, states the Weekly Stationary Engineer, lately been devised by Professor Rowland, of Johns Hopkins University, Baltimore, U.S.A. The requirements in this ca.so are that the screw should bo so perfect that 50,000 distinct and equidistant lines might be ruled within the space of 1 inch, and this Professor Rowland lias accomplished. The tests to which the work has been submitted show that the screw is so perfect that no imperfection can be detected. Many precautions were taken to prevent tho action of outside influences which would mar the accuracy of the results, The screw was cut in the workshop in the physical laboratory of the University on an ordinary lathe, and was afterward ground with line emery under water and oil maintained at a certain temperature for over three weeks. The grinding was accomplished by the use of a nut which extended over the entire length of the screw, tho nut being made as nearly perfect as possible, and this was moved to and fro constantly, the grinding taking place to a great extent 011 those parts which were out of true" until at last the perfect screw was formed. This screw is li inch in diameter, 17 inches long, and has twenty threads to the inch. The plates which are to be ruled with this large number of lines to tho inch are for use in spectroscopic work, where a variation in the distance between adjacent lines would be readily detected in the colours reflected from its surface. LOGS CUT WITH A KN'IKK. There was exhibited recently at Oreonpoint, L.1., says the New York Herald, a machine which it is thought may possibly revolutionise the lumber business. This machine cuts lumber without any wasta, and there is no sawdust whatever. In cutting lumber with a saw there is a great loss which goes into sawdust. Tho now invention, which is called the " Bradley Drawcutting .Machine," is designed to cut thin board;) and planks, and will cut in different thicknesses varying from one thirty-second of an inch to an inch. The inventor is Thomas S. Crane, and he has been ut work on it for five years. Tho saving of lumber that this machine will effect will be very great. Mr. Lewis said that in small lumber one-quarter and one-half inch in thickness, one quarter of the log is lost in sawdust. Then another eighth is lost in planing, and the lumberman in preparing his lumber for use. loses three-eighths of the log. This new invention will savo nearly all that. The machine was recently seen for the first, time. It. cut cherry, ash, birch, and maple in thicknesses from a sixteenth to a half inch. It. is intended to be placed in the woods and to cut the trees as soon as they are felled, Green wood is cut more easily than seasoned wood, but logs were cut that had lain in the yard ten years. The machine weighs forty tons. THE LAW OK GRAVITATION. Conceive that a traveller wero endowed with some means of soaring aloft for miles and thousands of miles, stiil up and up, until at length he had attained the awful height of nearly a quarter of a million of miles above the ground. (Glancing down at the surface of that earth, which is at such a stupendous depth beneath, he would be able to see a wonderful bird's-eye view, lie would lose, no doubt, the details of towns and villages; the features in such a landscape would be whole continents and whole oceans, in so far as the openings between the clouds would permit the earth's surface to be exposed. At this stupendous elevation he could try one of the most interesting experiments that was ever in the [lower of a philosopher. He could test whether the earth's attraction was felt at Mich a height, and he could measure the amount of that attraction. 'lake for the experiment a cork, a marble, or any other object, large or small; hold it between the fingers, ami let it go. Everyone knows what would happen in such a case down here, but it required Sir Isaac Newton to till what would happen in such a ease up there. Newton asserts that the power of the earth to attract bodies cxten ls even to this great height, and that the marble will fall. This is the doctrine that we can now test. Wo are ready for the experiment. The marble is released, and lo ! our lirst exclamation is one of wonder. Instead of

dropping instantly, the little object appears to remain suspended. We arc on the point uf exclaiming that we inu-t have gone beyond the earth's attraction, and that Newton is wrong, when our attention is ar- ! rested, the marble is beginning to move, so ! slowly that at lirst we have to watch it carefully. But the pacegiadually improves, so that the attraction is beyond all doubt, until, gradually acquit ing more and more velocity, the marble .speeds on its long journey of a quarter of a million of miles to the earth. —The Story of t.he Heavens." Till-: KM OF I.ARC,K SAILINK-SIIII'S. As indicating the magnitude and intricacy of the rig of the huge sailing-ships now in vogue and the extent to which the " tinbought wind' is taken advantage of even in ; his age of steam the folio wing general particidars respecting the M aria Rickmers, which have been supplied by .Messrs. Kus-,-i i 1 and Co., the owners of the vessel, will doubtless be of interest. The total sail area .a' the Maria 30,800 square feet, the aggregate length of sparring fitted to suspend and spread the same being 2000 lineal feet. The combined height of her five masts is DUO feet; the total length of steel wire, in the form of shrouds, stays, and spars, is 21,300 lineal feet, or over four statute miles ; and the total length of running cordage is no less than 31,000 lineal feet, or approaching six miles ! i.h; htmni; CONDUCTORS AT ska. A matter which has probably escaped attention is the absence of shipping reports as to damage by lightning. Formerly, when wooden ships were rigged ith cordage, there were numerous cases recorded of vessels having been struck by lightning with destructive results. What with increased sizes of hulls and consequent lengthening of masts, it might reasonably have been expected that there would have been greater risk, as the tapering musts are calculated to attract the electric discharge. It is suggested that the immunity is ac counted for by the fact that most ships have wire ropes, which serve as lightningconductors—the lightning travelling along the wire, through the iron hull, to the water. No instance can be found where a vessel so rigged has been struck and damaged unless the conducting circuit has been in some way interrupted. IKON' I'AI'KK. In tlio Great Exhibition of 1851 a sped-, men of iron paper was exhibited which had the effect of instigating a lively competition among ironmasters as to the thinness to which cold iron could bo rolled. One ironmaker rolled sheets the average thickness of which was the l-lSooth part of an inch — in other words, 1800 sheets of this iron, piled one upon the other, would only measure one inch in thickness. The wonderful fineness of this work may bo more readily understood when it is remembered that 1 '200 sheets of tissue paper measure a fraction over one inch. These wonderful iron sheets were perfectly smooth, and easy to write upon. MISCELLANEOUS. Dai.win's doctrine of natural selection is being more and more exposed as insufficient by scientific men. At the Victoria Ins. itute, under the presidency of Sir George Stokes, Bart., V.P.R.S., a paper was read by Mr. J. W. Slater, F.C.S., F.E.S., in which, after adducing many arguments and facts, he said that they justified this conclusion, " that natural selection or the struggle for existence is by no means the prime agent in genesis of species." A bifurcated apron for mechanics is a recent American idea, the raison d'etre of which is that; its use does not in the least interfere with the movements of the wearer in climbing or working in any position. Only one size of this apron is made, as it is adjustable and can bo made to fit any sized man. It is well made, of heavy canvas, and contains tool, nail, and foot-rule [sockets, and a single apron will last " a lifetime." One of the wonders revealed by the microscope is that human hairs possess a marked individuality. Nob long ago a single hair—the evidence in a murder case —was shown to Dr. Jeserich, with the request that he determine whether it was from the head of the supposed murderer, whose hair was of the same colour. After examination the specialist decided that it was sufficiently unlike those of the suspected man to acquit him. The real murderer was subsequently captured, and his hairs were found to be identical in character with the one first examined.