32 



SCIENTIFIC NEWS. 



[April 1st, I J 



room has been found for the charge, which now consists 

 of 70 lbs. of damp gun cotton. The original Woolwich 

 Whitehead torpedo carried only 23 lbs. of gun cotton. 



The great feature about the Whitehead torpedo is the 

 mechanism by which the depth at which it travels in the 

 water is provided for. It will be easily understood that if 

 the specific gravity of the whole weapon were less than that 

 of water, it would float at the surface, more or less out of 

 water ; while if the specific gravity were greater than water, 

 it would certainly sink, for there are no half measures 

 about flotation. It is this part of the apparatus which con- 

 stitutes the secret, and so important was this considered 

 that all persons who were entrusted with the details had to 

 make a declaration that they would not make them known. 



The Turkish Government did not purchase this secret from 

 Mr. Whitehead, but they became acquainted with it through 

 a torpedo being fired at their ships by the Russians, during 

 the Russo-Turkish war. This weapon missed its mark and 

 came ashore unexploded. It was taken possession of by the 

 Turks, who thus had au opportunity of studying its mechan- 

 ism without being under any engagement as to secrecy. 

 Lieutenant Sleeman was at the time in the Ottoman Navy, 

 and in his book on the torpedo he thus describes this part of 

 the weapon : " The torpedo is maintained at the desired depth 

 by means of certain mechanical apparatus contained within 

 the adjustment chamber, and which constitutes what is called 

 the secret of the fish torpedo. This chamber is connected by 

 screws to the foremost and after chambers of the torpedo in 

 such a manner that by means of a number of holes bored 

 round the circumference, the faces of the chamber are ex- 

 posed to the pressure of the water, which varies with the 

 depth lo which the torpedo descends. Within the adjust- 

 ment chamber is an endless strong spiral spring attached 

 to the after face of the chamber, and so arranged, that after 

 being set to a certain tension, capable of resisting an equi- 

 valent pressure on the outside of the aforesaid face, any 

 increase or decrease in this exterior pressure will cause the 

 spiral spring to work a rod by which the horizontal rudders 

 of the torpedo are regulated, and thus the desired depth for 

 which the spring is set is maintained. The course of the 

 torpedo is represented by a series of curves, above and below 

 the line, corresponding to the depth set for. These curves 

 gradually decrease, until at 100 yards' distance, they are so 

 small that the path is almost identical with a straight fine." 

 There is also fitted a swinging weight which assists the 

 action. 



The weapon can be adjusted to explode either by contact 

 with the side of the attacked vessel, or at the expiration of 

 a certain time. It can be set to travel at any depth between 

 five and fifteen feet. It can be arranged at will to either 

 float or sink at the end of a run, so that if it were set for 

 contact firing, and did not hit its mark, it could not be 

 captured by the enemy. At the same time it can be re- 

 covered after a practice run in peace time. The standard 

 speed for a modern Woolwich Whitehead torpedo is at the 

 rate of twenty-four and a half knots an hour, and it will 

 travel at this rate for 600 yards. It is said, however,* that 

 twenty-six knots has been reached for this distance, whilst 

 one torpedo ran for 400 yards at the rate of twenty-seven 

 knots an hour. It is needless to say that no vessel that ever 

 yet floated can attain this speed. 



The method of ejecting the fish torpedo from a vessel is 

 an important feature, and one on which its efficiency to a 

 great extent depends. In those wonderful craft, the torpedo 

 boats, which are built solely for operating with this weapon, 

 there are two methods of sending it on its errand of destruc- 

 tion. In the first a tube or gun is built into the structure of 



* See £k^;'«(;.W»^ of October 22ncl, i8S6, 



the vessel itself, the launching then being effected over the 

 bow. Our illustration shows a torpedo boat constructed by 

 Messrs. Yarrow and Co., the well-known builders of these 

 craft. The torpedo may be plainly seen in its berth, but 

 when the cover is shut it is snugly tucked away out of sight. 

 In the larger boats of this class two torpedo tubes are placed 

 side by side. The second method of firing is by torpedo 

 tubes, or guns, as they are generally called, being mounted 

 separately on deck. They are generally fixed on a turn- 

 table, so that they can be turned to point towards the 

 enemy without moving the boat. In the built-in system the 

 vessel itself must be manoeuvred to point to the object; 

 often no easy matter in a sea-way. 



The launching impulse can be given cither by com- 

 pressed air, steam, or gunpowder. There is a small 

 cylinder at the rear of the tube, and in this a piston works, 

 having a projecting piston-rod which is arranged to strike 

 the end of the torpedo when the launching is to be effected. 

 On the compressed air or steam being admitted to the 

 cylinder, or the gunpowder being exploded, the piston is 

 thrust forward, and the impulse is thus given. The gun- 

 powder method is the most recent, and is generally con- 

 sidered the most efficient system of launching. 



The reputation of the Whitehead torpedo as an engine 

 of destruction has been somewhat shaken of late, in conse- 

 quence of experiments made at Portsmouth on H.M.S. 

 Resistance, an obsolete ironclad which was condemned to a 

 species of naval vivisection in the interests of science. It 

 would take too much space to describe the trials that took 

 place:, but it will be sufficient to say that the torpedo failed 

 to actually sink the ship, although exploded in contact with 

 her side. This was altogether an unexpected result, and 

 naval men have begun to think lately that they have been 

 taking the enormous destructive powers with which the tor- 

 pedo has been credited a little too much on trust. Whatever 

 may be said, however, there is no doubt but that the fish 

 torpedo is a weapon of enormous possibihties, and no mari- 

 time nation can afford to neglect it. Whether these possi- 

 bilities could be realised in actual warfare, we hope will 

 remain for ever a sealed book. 



Electrical Resistance of Bodies when in the Magnetic 

 Field. — Dr. Jae has continued the experiments of Thomson and 

 Righi, which prove that the electrical resistances of iron and 

 nickel (paramagnetic or simply magnetic bodies) and of bis- 

 muth (the most strongly diamagnetic body) undergo sensible 

 changes, if the substances are placed in a magnetic field. There 

 appears to exist a connection between this phenomena and the 

 Hall effect. Dr. Jae used small antimony cylinders, with copper 

 wires soldered to the ends, and electromagnets excited by cells 

 or a dynamo. The cylinders were cast in little glass tubes, the 

 glass being afterwards removed by repeated cooling and heating. 

 When in the magnetic field the resistance was always increased, 

 independently of the direction of the current; but more strongly 

 in a transverse direction than along the longitudinal axis. 

 Cobalt was employed in the form of fine lamellte ; if their plane 

 was normal to the lines of force the electrical resistance de- 

 creased ; if held parallel to the lines of force, and so that the 

 current had the same direction, there was an increase. Thus 

 the antimony sides with the bismuth, and the cobalt with iron 

 and nickel, as analogy would lead one to expect. — La Ltuniere 

 Elcctriquc, January 23rd, 1887. 



A Phantom Army. — In Vidovec, a Hungarian village near 

 Warasdin, the belief of an approaching war has seized hold of 

 the entire population. A splendid Fata Morgana was observed 

 during three consecutive days on the wide plains around the 

 village. Infantry could be seen performing exercises. The 

 phenomenon lasted several hours, and finally the soldiers 

 disappeared in mid-air. 



The fastest run yet made across the Atlantic was accomplished 

 by the Etruria last month. The time occupied was 6 days 6 

 hours and 18 minutes. 



