MECHANICAL AND SCIENTIFIC NOTICES.

Otago Witness, Issue 134, 10 December 1853, Page 3

MECHANICAL AND SCIENTIFIC NOTICES.

Cameron's New* Patent Compass. — The follow- | ing is a short description of the Variation and Distance Compass, lately patented by Mr. Cameron, which we consider calculated, when once known, to supersede most, if not all the instruments at present in use for marine and land surveying purposes : — The exterior form of Mr. Cameron's Marine Compass is similar to those at present in use, but there are various improved arrangements and additions connected with it which require to be noticed. The j first of these refers to the compensation for the ".ibrating motion of the compass-card. By having attached a brass rod with a ball at each end, one ball being fitted into a socket in the bottom of the com-pass-case, while the other, which is larger, swings ! upon the rod which is affixed to the upper ball as a centre, the oscillations are speedily checked. Again, one half of the compass-card is divided into a series of triangles, the edge of the needle being graduated, so that as the needle works round o\er the triangles, the mariner may at once see his actual route on comparison with the distance run. To the centre of the compass-card or needle is attached a small vertical style, so that the shadow of such style being compaied with the dial-table, furnishes a means of at once ascertaining the magnetic variation. To the north pole of the compas&-box is fixed a brass, frame, containing a slip of glass divided into degrees of the tangent, and one of the sides of the brass frame is divided into a line of numbers, which give the altitudes conesponding to a ba?e of 100, which may be increased or diminished by multiply-, ing or dividing, according to the proportion of the numbers. To the south pole of the compass-box is fixed a small telescope, with cross sights, for reading oft" the degrees of altitude and heights of objects, so that the compass ma} be applied in taking azimuths and altitudes, and in all ordinary purposes of measurement and surveying. For the purpose of rectifying, the compass is suspended within a brass ring, the exterior of which is grooved, and has a tangent screw working in it, so that by this screw the compass may be set to the magnetic meridian at any time. Round the compass-case there is a copper correcting-ring, for the purpose of checking the vrbrations of the needle, which can be easily adjusted to the size, and strength or weakness of individual needles. It is hardly possible to over-estimate the importance of this invention. From a series of tables which Mr. Cameron has drawn up to facilitate the use of his compass, the mariner has it in his power from a simple observation to determine the latitude and longitude, and also to check his chronometer. For instance, should the latter all important instrument have gone wrong, or should it have altogether ceased to work, Mr. Cameron's compass will, at twelve o'clock on any day, show apparent time, and thus enable the most inexperienced person to start the chronometer at any point of the earth's surface. We trust that this instrument may speedily come into use in every ship, because, while it is unfailing in its indications, it must greatly lessen labour and secure accuracy in marine calculations. On the Preparation of Liquid Glue. — All chemists are aware, that when a solution of glue (gelatine) is heated and cooled several times in contact with the air, it loses the property of forming a jelly. M. Gmelin observed that a solution of isinglass, enclosed in a sealed glass tube and kept in a state of ebullition on the water-bath for several days, presented the same phenomenon— that is to say, the glue remained fluid, and did not form a jelly. The change thus produced is one of the most difficult of solution in organic chemistry. It may be supposed, however, that, in the alteration which the glue undergoes, the oxygen of the air or of the water plays a principal part ; which leads me to think this is the effect produced upon glue by a t small quantity of nitric acid. It is well known, that by treating gelatine with an excess of this acid, it is converted by heat into malic and oxalic acids, fatty matter, tannin, &c. But it is not thus when this glue is treated with its weight of water and with a small quantity of nitric acid ; by this means a glue is obtained which preserves nearly all its primitive qualities, but which has no longer the power of forming a jelly. Upon this process, which I communioated, is founded the Parisian manufacture of the glue which is sold in France under the title of

'• colic liqiiide et inalterable." This glue being- veryconvenient to cabinet-makers, joiners, pasteboard! workers, toy-makers, and others, as it is applied cold, I think it ray duty, in order to increase its manufacture, to publish the process : — It consists in taking 1 kilog. of glue, and dissolving it in 1 litre oS water in a glazed pot over a gentle tire, or, what is better, in the water-bath, stirring it from, time ta time. "When all the glue is melted, 200 grms. of nitric acid (spec gray. 1.32) are to be poured in, in small quantities at a time. This addition produces, an efferveseace, owing ta the disengagement of hyponitrous acid., "When all the acid is added, the vessel is to be taken from, the fire, and left to cool. I have kept the glue thus prepared in an open vessel during more than two years, without its undergoing any change. It is very convenient in chemical operations ; I use it with advantage in ruy. laboratory for the preservation of various gases, by covering strips of linen with it. — M. S. Damoulin z Compteß Rendus.

Receipt foe. Joixi.vg Glass. — Melt a little isinglass in some spirits of wine, and add a small quantity of water. Warm the mixture gently over a moderate tire. When mixed by thoroughly melting, it will form glue perfectly transparent, and which will re-unite broken glass so- nicely and firmly that the joining will scarcely be perceptible to the most critical eye. Lime mixed with the white of an egg forms a very strong cement for glass, porcelain* &c, but it must be done neatly, as, when hard, thesuperfluous part cannot easily be smoothed, or, takeu, off. — Scientific American. Ax Experiment. — The New York Tribune says, —Singular results are obtained in this city from a j very simple application of the nervous fluid, animal j magnetism, or whatever be the agency, to brute matter. Let a party of six or eight persons sit around a common pine table for 20 minutes to half an hour, with the palms of the hands held flat on the top of the table ; it is not necessary that theiy minds should pay any attention to the process, of conversation be suspended ; but presently the table- | becomes so charged with the mysterious fluid that it I begins to move ; then rise from it, push away your chairs, still holding your hands near, though it is not necessary to touch it, and it will turn around from end to end, and even proceed rapidly about the room, without any visible agent, on which excursions the persons must bear it company,, or the current is broken and the movement stops. This simple expeiiment may easily be tried; it requires no j faith and no outlay of physical or moral strength ; and the result, with a table that is not too heavy, i* pretty sure to follow. Taule Moving. — The Manchester Guardian states that a conversazione took place in that tow« on Thursday evening, on the subject of table movj ing and its causes ; the Rev. 11. H. Jones, F.R.A.S., in the chair. — Mr. "W. G. Gintz moved the appointment of a committee, to have direction of the experiments and to report upon them, which was agreed to. The experiments commenced at 8 o'clock, and lasted upwaids of three hours, and duiing that pc- , riod several tables were turned round with considerable telocity; but, on the contrary, other experi- , ments v.ere decidedly unsuccessful. — After the , performance of these experiments, Dr. Braid said | theie had been some most unexceptionable experiments. They had seen two tables turn, and his con\iction was that the motion arose from what Dr» Carpenter called the ideo-moter power. The mind being concentrated for a length of time upon an idea, it at last began to act upon the muscular system. This was not h voluntary act, and might even be in opposition to volition. He was satisfied, sufar as he had seen, that this was the true solution of the matter ; that the ladies and gentlemen were not conscious that they exercised any effort, and that the effect arose from this unconscious muscular action. In order to test whether or not the motion was caused by electricity, he suggested that a \ure should be laid upon the tables, and that instead of touching the table the experimenters should hold this wire. If the motion arose from electiicity, it would take place under these circumstances ; if it was the result of muscular action, the effect of that action would be on the wire, and not on the table. The experiment was accordingly tried. A piece of thin wire was laid round the ladies' table. They maintained their positions for half an hour withoutsuccess, and then abandoned the attempt. They -then placed their fingers upon the table, and in about a minute it turned rapidly. — The chairman, before leaving the chair, said that he had come into that room without any prejudice ; but that, from what he had seen and heard, he believed that the phenomena resulted entirely from muscular action, by the power of friction. — Dr. Braid, in moving a vote of thanks to the chairman, said that, if we considered the reciprocal action of the mind upon matter, we had a key to the whole mystery. It was a certain law that the mind, being concentrated for any length of time upon any part of the body, changed the physical action of that part. If there was an idea that the table should move in a given direction, that idea would, without a conscious effort of volition, without the person beiieving that he was exercising any effort at all, produce the effect. — The vote of thanks was unanimously adopted, and the proceedings terminated.

One of the latest experiments of the " tablemoving" mania, or Tavola-inorbiu, was performed on board of a vessel in the London docks, which was swung round simply by the sailors forming a magnetic trhain and pressing their hands on the deck !

Shout Weigjett.— A cottager^ who recently had his butter seized for short weight, pleaded in escns^ that the cow from which the butter-wan made wa* subject to the cramp, and that caused the butter to shrink in weight. The Slandekeb.— " If there is any<bo.dy under the canister of heaven that I have in utter excrese," says the amiable Mrs. Partington, "it is the slanderer, going about like a boa censtructor, .circulating bis calomel about honest folks."