NOTES ON SCIENCE, MECHANICAL INVENTIONS, ETC.
REGULATING THE SPEED OF ENGINES. A method of regulating tho speed of gas and other engines for driving dynamos has been devised. In this system the supply of gas to the motor is controlled electricallly by means of a solenoid coupled up with the lamps, either in series or in parallel, according as a constant potential or a constant current service is required. A soft iron core is placed in the solenoid, and any variation of the current in the latter causes a corresponding change in the position of the core. The core is connected by a lever to the gas valve, the opening through which is thus varied, pari passu, with the current through the coil. This is so arranged that the greater the load on the dynamo the wider is the gas-valve opened, with the curious result that the speed of the engine is greater \uidei high loads than under low. A DYNAMITE GUN. The Pneumatic Dynamite Gun has lately been subjected to some very exhausti\e trials at Fort Lafayette, New York. Hie Secretary of the United States Navy had placed at the disposal of the company which has been formed for dealing with this weapon an old schooner, which was moored at about two thousand yards from the fort. After two shots of blank shells had been tired, in order to find the range, the gun was loaded with a charge missile containing fifty-live pounds of explosive gelatine. 'I lie result of this shot was to give the old vessel a terrible shaking, and, as was discovered by those who boarded her immediately after he explosion, toinjure her severely and cause serious leaks. With succeeding shots the vessel was broken up into matchwood. A photograph taken instantaneously, just as one oJ these explosions occurred, shows the vessel with the hull raised up several feet above its normal posit ion. This picture thus exhibits in a curious manner the peculiar lifting-power of the explosive employed. A writer in one of our service journals maintains that some kind of international agreement will have to be come to " for the prompt execution of the inventors of now weapons otherwise, he urges that the whole naval question will be once more upset, and millions must, be spent in a new direction. This reminds us that " there are many true words spoken in jest." an ideal boii.ei:. An invention is announced which, if the accounts given of it are free from any verygross exaggeration, must work a revolution in the applicability and in the cost of mechanical motor-power. The inventor avers that he can reduce the ordinary demand for boiler space by no less than Of! per cent. ! The method proposed is the substitution of a small copper boiler for the large iron boilers now in use. A cylinder of copper, of IT, inches in diameter and '20 inches long, has a hemispherical end, in which are placed loosepieees of broken copper. At the opposite end of the vessel two pi pes are introduced —one to lead in the water, the other to lead out the steam. Through the first pipe the water is forced so as to spread in a fine spray over the broken copper, which, it. is said, immediately converts it. into steam . The chief consideration which would lead any practical man to make inquiry into the inventor's claims is this : the conductivity of copper is unusually high, being more than six times that, of iron. If it be possible— which we are not in a position to deny— to make a more efficient use ot this property of the metal than has hitherto been done, a reduction of bulk might, no doubt beetleeted. On the other hand, no such difference has been usually attributed to the calorific power of copper and ot iron tubes in the boiler of the locomotive ; and, while copper kettles and saucepans are the pride of the housekeeper, we should be disposed to say that water in a tin kettle boils faster than in a copper one. These, however, are mere reflections on the first account of the matter, leading to the conclusion that the claim made is neither i/wo facto absurd nor, on the other hand, extremely probable. Another consideration is that if copper can thus drive iron from the field, it may in its turn be dispossessed by silver. Taking the heatconducting power of silver at 1000. that of copper is 7.';ti, and that of iron 110, lead being as low as S,~i. If a six-fold efficiency is thus attributable to the thermic conductivity of copper, allowing the engineer to reduce the area of the copper boiler (aided by that of the loose pieces of copper), to a sixth of that of an iron boiler, by the use of silver instead of copper the gain may become nine-fold instead of six-fold. It is not, however. by speculation but by exhaustive experiment that the now claim is to be tested. An enormous stimulus- would be given to the mechanical use of steam as a motorpower if the most cumbrous part of the machinery could be reduced in anything like the above-indicated ratio. The inventor is said to claim an economy of si> per cent, in fuel. The margin between the theoretic power to be obtained from the combustion of a given weight of carbon and the efficiency of even the best compound engines is such as to allow of a much greater gain to the consumer than ~>o per cent. But the gain in the cost, size, and weight of the new boilers could it be established, would be of far more importance than the economy per horse-power of the force produced. The application of steam-power to locomotion is now limited by the size and weight of the boiler. Efforts so to reduce this part of the machinery as to render the cost of its carriage a less absorbing item in the whole cost, of transport of freight or passengers have been constant for halt a century. But advance has been made not in the way of diminishing the weight and power of the machine, but of increasing the volume and 1 weight of the load. If the account we have quoted be only half true, we may expect the evolution of a swarm of steam tricycles. For those machines a silver boiler heated by petroleum may be suggested ; or, rather, a cylinder of aluminium bronze, on account of its enormous tensile strength, with conducting plates of silver. ! LOFTY ASCENT. An attempt has lately been made at ! Paris by MM. Jovis and Mallet to rise to a . greater height in the atmosphere by means of a balloon than has ever yet been done. I The aeronauts took with them a number of
instruments for the purpose of making observations, and among these were a barometer designed to measure heights of upwards of thirty thousand feet, and a thermometer which would record temperatures fifty degrees below zero. A new feature was represented by the provision of bags of oxygen, for the purpose of inhalation by the aeronauts after attaining high elevations. It will be remembered that in 1862 Messrs. Glaisher and Coxwell ascended from Wolverhampton for the purpose of making scientific observations from a balloon, and that they then reached tho extraordinary altitude of seven miles above the earth. On this occasion both the occupants of the car suffered very much, Mr. Glaisher becoming quite insensible for a time. A similar experience seems to have been the lot of thetio French experimenters, one of them, having fainted twice upon reaching tho altitude of twenty thousand feet, tho faintness being speedily mitigated after inhalation of the oxygen provided. The ascent was successful, but the height reached was far below that attained by Mr. Glaishcr and his companion, as already recorded. A RIVAL OF THE NIONOGRAI'II. The announcement is made, says the New York correspondent of the Daily News, that Mr. Bell, the inventor of the telephone, has patented an instrument called the " Graphophone," very similar to Mr. Edison's phonograph. The chief difference between the phonograph and the graphophone is that while in the former the electric motor moves a cylinder at a prescribed speed, in the latter the motion is imparted by a series of wheels geared to a treadle worked by the foot as in the sewing machine. An ingenious governor regulates tho speed. The Graphophone Company expect also to provide a motor moved by clock weights. Any mechanical power of this kind has been preferred to electric batteries. The wax cylinders used for impression are all about the same size as Mr. Edison uses. The cost of the graphophone will be, according to the persons interested in it, far less than the phonograph, owing to the elimination of the electric motor and battery. The instrument itself can be made for less than ten dollars, and probably will be sold, table and all, for about 25 dollars. During the last six months several workmen have been employed upon the machines in the laboratory of the Bell Company at Washington, and it is thought they will be ready for the market some time within the next sue weeks.