March 6, 1879] 



NATURE 



415 



it seemed to me that even supposing that the second 

 charge had been ignited by the first, which was doubtful, 

 this would not explain the suddenness or magnitude of 

 the pressure. But on further consideration it appeared 

 certain that the second charge would not be ignited by 

 the fire from the first ; and it then became clear that in 

 this very fact we should have an amply sufficient explana- 

 tion of the excessive pressure. 



My object in writing this paper is to point out the pro- 

 bability of this explanati jn, and so, if possible, to induce 

 the authorities to test it. It occurred to me several days 

 before the report of the Committee appeared, and in 

 spite of the improbability of such a mistake as double 

 loading, I could not shake off the conviction that it 

 afforded the true explanation. As I have pointed out, 

 the blowing into fragments of a wrought-iron tube im- 

 plied an explosive action such as might result from gun- 

 cotton or dynamite, but which could not be produced by 

 the slow burning of pebble powder. The point to be 

 explained, then, is how the second charge could be 

 brought into such a condition that it would explode like 

 gun-cotton. To understand this, it must be remembered 

 that in the usual way the grains of gunpowder burn from 

 their outside only, so that the thicker the grains the 

 longer will be the time occupied in burning, and for the 

 same weight of powder the slower will the gas be given 

 off. The reason why gun-cotton is so much more de- 

 structive than gunpowder is not that it gives off more 

 gas weight for weight, but that when ignited by a flash it 

 burns so much quicker. If, therefore, by any means the 

 whole miss of gunpowder coull be heated up to the 

 firing point at the same instant, so that the grains fired 

 simultaneously inside as well as out, the action of the 

 powder would be as quick or quicker than the gun-cotton. 

 And, still further, if basides being heated the powder was 

 compressed into a fraction o: the space it usually occu- 

 pies, the gases so confined would be capable of a still 

 greater pressure. 



Noy if the after cartridge were fired and the forward 

 cartridge were not ignited by the flash, and considering 

 the length atid fit of the shot, it could hardly have been 

 so ignited, then the after shot would be driven forward 

 closing on to the forward shot and compressing the 

 powder between until the pressure on the for'^ard shot was 

 at least half as great as the pressure of the gases behind the 

 after shot, which would be between ten and twenty tons 

 on the square inch. Thus the powder would be subjected 

 to a squeeze between the two shot such as would result 

 from a blow. It would be compressed to a fraction of 

 its former volume. The cubes would be crushed into a 

 cake and the work of compression would be sufficient to 

 heat the powder far beyond its point of ignition. Thus 

 the entire mass of powder would be simultaneously ignited 

 in a highly compressed and heated state. The force of 

 such an explosion would be practically unlimited and 

 would be located at the very point at which the gun 

 burst. Hence in such an action we have ample cause for 

 the effect produced. 



But it will be asked why does not the same thing 

 happen when a rifle is doubly loaded? It is said that in 

 that case the second cartridge is generally blown out 

 before it ignites, and this may be so, for in the rifle the 

 intensity of the pressure of the gas on the shot can never 

 exceed above a twentieth part of what it is in the 12-inch 

 gun, and hence in the case of the rifle the pressure may 

 well be insufficient to ignite the powder between the shot. 



This view of the action resulting from the firing of 

 powder by percussion appears to me to be one which it 

 would be well worth while to test, for if proved it would 

 completely re-establish confidence in the strength of the 

 guns, which has been somewhat rudely shaken. 



Let a 12-inch gun be loaded with a double charge of 

 powder and a double charge of shot, or a shot of double 

 weight, and fired. If, as is probable, the gun does not 



burst, confidence in the gun will be re-established. Then 

 let it be loaded twice over with the powder between the 

 shot so as to ascertain whether the action of the powder 

 when fired by percussion would not produce an effect 

 similar to that which we are here considering. The 

 destruction of one gun for the purpose of establishing 

 confidence in all the rest would not seem to be an un- 

 worthy sacrifice. 



MOSELEY'S NATURALIST ON THE 

 "^ CHALLENGER" '*■ 



THIS is certainly the most interesting and suggestive 

 book, descriptive of a naturalist's travels, which 

 has been published since Mr. Darwin's "Journal of 

 Researches " appeared, more than forty years ago. That 

 it is worthy to be placed alongside that delightful record 

 of the impressions, speculations, and reflections of _ a 

 master-mind, is, we do not doubt, the highest praise 

 which Mr. Moseley would desire for his book, and we do 

 not hesitate to say that such praise is its desert. The 

 same argus-like power of observation, the same readiness 

 to appreciate the true interest and significance of every 

 seemingly Uttle fact, the same energy and indomitable 

 perseverance in gathering information and material fironi 

 every source in the short space of time at the circum- 

 navigator's disposal which distinguished Mr. Darwin, 

 characterise also his disciple and follower in many a 

 distant ocean land and tropical forest. 



Before the Challenger expedition set sail, Mr. Moseley 

 was known as an accomplished biologist, trained in the 

 laboratories of Strieker, of Vienna, and of Ludwig, of 

 Leipzig. He had taken part in the eclipse expedition to 

 Ceylon, and besides making valuable spectroscopic obser- 

 vations on the sun, had found time when there to study 

 and collect specimens of the land Planarian Worms, the 

 structure of which was the subject of a memoir by him in 

 the Philosophical Transactions (published after the 

 Cfiallenger hdid left in 1874) which threw altogether new 

 light on such important matters as the nature of meta- 

 meric segmentation and the origin of the blood-lymph 

 space, coelom, or body-cavity of higher organisms gener- 

 ally. 



During the C^a//^«^^r expedition, and since its retxmi in 

 1 876 (when he was by special statute elected to a "research" 

 fellowship by the members of his old college of Exeter, in 

 Oxford), Mr. Moseley has, apart from this volume and 

 its varied contents, produced a series of original memoirs 

 published chiefly by the learned societies of London, 

 which have been the means of making known the most 

 important of the results to which the Challenger expedi- 

 tion has led in the field of biological science. It is to his 

 industry and skill, combined with the opportunity afforded 

 by the Challejiger' s cruise, that we owe the thorough 

 description of the anatomy of the worm-like land-living 

 Peripatus, and its development, studied by him at the 

 Cape of Good Hope {Philosophical Transactions, 1874), 

 whereby a totally new light is thrown upon the relation- 

 ships of the great group of Hexapodous and Myriapodous 

 insects, and the origin of tracheae ; to him we are in- 

 debted for the discovery and description of .the most 

 remarkable among the many pelagic or surface animals 

 taken by the Challenger on the high seas, the transparent 

 Pelagonemertes {Annals and Mag. Nat. Hist., 1875), a* 

 well as for the detection of the only really markedly aber- 

 rant form of life dredged by the Challenger in deep waters 

 {Linnean Transactions, 1878), the Ascidian, Octacnemus 

 bythius. The colouring matters, also, of various manne 

 animals have been studied by him with the spectroscope 

 and the spectra, carefully recorded in the Quart. Joum 

 Microsc. Sci. 1 877. But of still greater importance and merit 

 was Mr. Mosele/s study of corals allied to Millepora and 



« Notes by a Naturalist on the Challenger. By H. N. Moseley, M. A., 

 F.R.S., Fellow of Exeter CoUige, Oxford. 



