March i6, 1876] 



NATURE 



395 



3. Aug. 3.— Near the top of the Rotang Pass (13,000'), 

 about 9 o'clock a.m., the lower half of a beautifully- 

 coloured ring was seen for about half an hour. 



4. Aug. 5.— Gondla (io,ooo')- At 3 p.m. a beautifully, 

 coloured ring round the sun was seen on a very thin film 

 of clouds in front of the sun. The blue was most dis- 

 tincc, and much purer than in the common rainbow. 



5. Sept. 19. — While going down the Jehlum in a boat 

 from Islamabad to Srinagur, I saw in the river the reflec- 

 tion of part of a coloured ring. Looking directly at the 

 cloud, I saw the ring again on the white edge of a cloud. 

 The sun was nearly setting, 



6. Sept. 23. — At Baramula, at 4 P.M., I saw the same 

 ring described above most distinctly, and making a com- 

 plete circle round the sun. 



7. — Marching out of Cashmere 1 was struck one morn- 

 ing by the appearance of the cloud being nearly the same 

 as when I had before seen the circle in question. On 

 looking carefully I could indeed see a faint trace of the 

 ring. 



8. Oct 6.— At Pcshawur (Punjab) I saw to the right of 

 the setting sun about the sixth part of the coloured ring. 



Arthur Schuster 



VISIT OF THE CHEMICAL SOCIETY TO THE 

 ROYAL ARSENAL 



IN response to an invitation from its president, Prof. 

 Abel, F.R.S., the chemist of the War Department, 

 nearly 500 Fellows of the Chemical Society visited the 

 Royal Arsenal at Woolwich on Tuesday last. The presi- 

 dents of most of the learned societies, together with other 

 eminent men of science, were included in Mr. Abel's 

 liberal invitation, so that during the day a constant stream 

 of visitors flowed through the interesting workshops at 

 Woolwich. 



Beyond the ordinary attractions of the establishment, 

 Mr. Abel had arranged to demonstrate the more import- 

 ant applications of science to warfare, and among these 

 were included some experiments with gun-cotton and 

 other explosives, the study of which he has made pecu- 

 liarly his own. Indeed, the most attractive part of the 

 programme from a scientific point of view was that carried 

 out on the outskirts of the arsenal in the vicinity of the 

 proof butts, where operations commenced by the firing 

 of the big 80-ton gun. Col. Younghusband, F.R.S., 

 R.A., the Superintendent of the Royal Gun Factories, as 

 well as other heads of departments, had entered warmly 

 into the spirit of the visit, and took considerable pains 

 that every opportunity should be given the Fellows of 

 witnessing the capabilities of this monster weapon. A 

 charge of 250 lbs. of gunpowder, the grains of which mea- 

 sured nearly two inches cube, was introduced into the 

 gun, and then the heavy bolt, or projectile, weighing 

 1,260 lbs. was rammed home. Those who were privileged 

 to enter the chronoscope room, which is so small unfortu- 

 nately, that scarcely a score of visitors could find room in 

 it, were gratified with a sight of Boulanger's instrument 

 for calculating the velocity of a cannon-ball in its flight, 

 and as the thundering discharge was heard, this 

 delicate apparatus proclaimed, simultaneously, that the 

 projectile had been sent on its way at a velocity of 

 nearly 1,500 feet a second, an impetus, it is said, 

 sufficient to make a hole through the Infiexible iron- 

 clad, with her twenty inches of armour and thick teak 

 backing. The Boulanger instrument is easily explained. 

 Placed in front of the gun, at an interval apart, are two 

 wire screens, so arranged that the projectile in its flight 

 tears through them one after another. From two magnets 

 attached to the instrument hang two metal rods, and the 

 instant the first wire screen is torn by the shot, a current 

 of electricity is broken and the first of these rods falls. 

 As No. I is in the act of falling, however, the second wire 

 screen is broken by the shot releasing No. 2 rod, and this 



sets in action a trigger which strikes No. i rod before it 

 has yet completed its fall. If the shot has been slow in 

 travelling from one screen to another, then rod No. i has, 

 naturally enough, nearly fallen its entire length before it 

 receives a stroke from the trigger ; and the higher the 

 mark is upon the rod No. i, or in other words, the more it 

 has fallen the less rapid has been the passage of the shot. 

 After the mark is made one has merely to refer to a scale 

 to get the velocity. 



After the firing of the 80-ton gun came the gun-cotton pro- 

 gramme, which Mr. Abel and Mr. E, O. Brown had arranged 

 for the purpose of demonstratingin the first place the peculiar 

 qualities of this explosive, and secondly its application to 

 war purposes. To quote from this programme, Mr. Abel 

 first gave " illustrations of some of the conditions which 

 promote detonation of an explosive agent by a blow, or by 

 the force exerted by an initial detonation." It was shown 

 that gun-cotton refused to detonate except under very 

 special circumstances, that is to say, neither a confined 

 charge of gunpowder nor a small charge of unconfined 

 mercuric fulminate brojght about that result, which was 

 only effected by a confined charge of fulminate, or by 

 other masses of gun-cotton being detonated in its imme- 

 diate vicinity- 

 Mr. Abel then went on to demonstrate the high speed 

 at which detonation travels, the same being faster than 

 any known agent, if we except electricity and light. A 

 row of gun-cotton cakes half an inch apart, 36 feet long, 

 was detonated at one end, and by crossing the row with 

 several insulated wires connected with Noble's chrono- 

 scope (the wires being broken one after the other, as the 

 detonation proceeded), it was proved that the velocity of 

 the detonation exceeded 18,000 feet per second. 



But it was the last of the gun-cotton experiments which 

 proved the most interesting to the general body of visitors, 

 as they illustrated the important uses of this valuable ex- 

 plosive. In these trials the gun-cotton was employed for the 

 most part in a loet, and therefore uninflammable state, in 

 which condition it detonates just as readily as when dry, 

 provided a small charge of desiccated cotton is used to start 

 the action. First of all, the value of detonation was shown 

 in connection with cavalry raids in an enemy's country. 

 Provided with a few pounds of gun-cotton and some 

 fulminate fuses, a trooper might cut half-a-dozen lines 

 of railway with very little ceremony, for, as Mr. Abel 

 plainly showed, an eight ounce cake of the material 

 exploded upon a rail, fractured the metals so com- 

 pletely as at once to block the line. In the demoli- 

 tion of wooden stockades, such as have caused us some 

 difficulty in Perak lately, gun-cotton wus shown to be 

 equally efficacious, for a charge of wet cakes placed at 

 the foot of such a structure on Tuesday last, levelled the 

 same to the ground far more quickly than it takes to tell 

 of the incident. Finally, a torpedo was fired under water 

 constructed in the most primitive manner, by simply 

 filling a large potato-net with gun-cotton slabs, and 

 throwing it bodily into the water, a fuze and dry primer 

 being contained in the middle of the charge. 



After lunch, which the president had hospitably pro- 

 vided for his numerous guests, and at the close of which 

 Dr. Hooker, C.B., P.R.S., took the opportunity of thank- 

 ing Mr. Abel for the intellectual treat he had provided 

 them with, the visitors had the satisfaction of witnessing 

 the process of big gun making, a forging of fifty tons of 

 glowing metal (the coil of one of the 80-ton guns) being 

 worked under the monster 40-ton steam-hammer for their 

 especial behoof. 



The last sight of all was certainly not the least in- 

 teresting. It was the run of a Whitehead torpedo under 

 water, the machine, as our readers may know, being 

 shaped in the form of a cigar and propelled through the 

 water, rocket-fashion, by means of compressed air, which 

 issues from its tail The passage of this submarine 

 monster the whole length of a canal, termed the torpedo 



