234 



SCIENTIFIC NEW^S. 



[Mar. 9, i8SS. 



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ROYAL UNITED SERVICE INSTITUTION. 

 On the 27th Jan. Captain H. de H. Haig, R.E., delivered a 

 lecture on the Pneumatic Dynamite Gun. He said small 

 charges of dynamite and gun-cotton had been fired in 

 projectiles, but usually such experiments had resulted in 

 the premature explosion of the shell in the bore and the 

 consequent destruction of the gun. The idea of propel- 

 ling such shells by means of compressed air was first 

 worked out by Mr. Mefford, of Ohio, United States, who 

 constructed a gun for the purpose and submitted it for 

 trial by the Government at Fort Lafayette, New York 

 Harbour, in 1884. The task of experimenting with this 

 weapon was entrusted to Lieutenant Zalinski, of the 5th 

 Artillery, who, while experimenting to ascertain the best 

 means of exploding his shells made the discovery that 

 very much greater results were obtained when the charge 

 was exploded from the rear than when the initial point 

 of ignition was in front. This was explained by con- 

 sidering that the charge took a short interval of time to 

 explode, and when the initial point was in front the 

 remainder of the explosives was blown backwards by 

 the gases first developed, and vice versa. The next 

 difficulty was a satisfactory fuse, which would explode 

 the shell whether it struck a ship or fell into the sea. 

 The requirements were — the impossibility of a prema- 

 ture explosion in the bore of the gun ; the certainty of 

 exploding the charge from the base of the shell on 

 striking any hard substance; and the certainty of explod- 

 ing the charge if the shell fell into the sea. He solved 

 the problem by placing two electric circuits in the shell, 

 the motive power being small chloride of silver batteries. 

 Either of these circuits when closed and complete would 

 cause a current to pass through a detonating fuze in the 

 base of the shell. The current heated a short piece of 

 platinum wire, which set oft' the detonating composition, 

 and it in turn exploded the charge. These two circuits 

 were kept open and incomplete until the right moment, 

 thus the first one had a gap in its circuit in the front of 

 the shell which could not be closed before the whole 

 contents of the shell moved bodily forward, and this 

 could only happen on its motion being suddenly arrested 

 by some hard substance ; the second circuit was complete, 

 but the battery was dry, and there was consequently no 

 current; sea-water penetrated through a hole in the shell, 

 wetted the cotton-wool in the cells of the battery, and 

 thus started the current, which fired the shell as described. 

 The Sin. gun, mounted at Fort Lafayette, threw a shell 

 containing loolb. of explosive to a distance of 3,000 

 yards, with an elevation of 33deg. and a pressure of 

 ijOoolb. The projectile was made of drawn brass or 

 mild steel, with a solid head, to get the centre of gravity 

 well forward. As the pressure in the bore was very 

 small it was a desideratum to get the shell as light as 

 possible, and so the walls were made very thin. It was 

 necessary for accuracy, however, that the projectile 

 should revolve about its longer axis, and to make it do so 

 a tail of wood, with spiral wings or feathers at the end, 

 was attached to it, giving it somewhat the appearance of 

 an arrow. The first shells used had long tails like 

 rockets, the centre of gravity being very far forward 

 owing to the cast iron head ; they flew fairly well. The 

 primary object of the gun was to throw what was prac- 



tically a torpedo, and its chief field of action was the 

 hull under the water. As regarded accuracy of fire the 

 pneumatic gun was very satisfactory. The cruiser now 

 being built for the United States Government is to 

 carry three of these guns, two of io| in. and one of i2| 

 in. The io| in. shell will contain 20olb. of explosive 

 gelatine, equal to 3nolb. of dry gun cotton, and the i2i in. 

 4oo]b., or equal to 6521b. of the same explosive. The 

 new guns will be of bronze, mounted on improved 

 carriages, and will have novel arrangements for load- 

 ing. One man will be able by the movement of 

 a single lever to open the breech, cause a projectile to be 

 placed in the bore, close the breech, and put another 

 projectile in position for loading. 



GLASGOW GEOLOGICAL SOCIETY. 

 On February i6th a meeting was held, at which Pro- 

 fessor Sir William Thompson read a paper on " Polar 

 Icecaps and their Influence in Changing the Sea Level." 

 It might be found, he observed, that the most probable 

 explanation of some changes of sea level, familiar 

 almost to people who were not geologists, was the sup- 

 position of the shiftings of ice either on the Antarctic 

 hemisphere or from the Antarctic to the Arctic regions. 

 The extent of the Antarctic hemisphere, according to Dr. 

 John Murray, of the Challenger, was about one-fortieth of 

 the whole area of the earth. In the event of 1,200 ft. of ice 

 on that hemisphere flowing into the water, it would raise 

 the sea level all over the world to the extent of 25 ft. The 

 latest change on the Firth of Clyde, which probably 

 dated back not many thousand years, was only 10 ft., 

 and consequently involved only 400 ft. of difference on 

 the Antarctic ice. In illustration of this subject he ex- 

 hibited pieces of a pine tree found embedded in floe-ice 

 in a Siberian river, after having come across the North 

 Pole. Of course, there might be islands about the North 

 Pole, though there was no reason to say so, but there 

 was certainly a great quantity of water which had a free 

 flow under the ice. It was possible that the land sloped up 

 to the South Pole to such an extent as to be clear of snow. 



EDINBURGH UNIVERSITY CHEMICAL SOCIETY. 

 At the meeting held on the 15th of February, Dr. J. 

 Gibson gave a lecture on " Spectroscopic Analysis," and 

 Mr. King communicated a paper by Mr. T. R. Marshall, 

 B.Sc, on " Fractionation as a means of obtaining pure 

 beryllium compounds." 



ROYAL PHYSICAL SOCIETY OF EDINBURGH. 

 At the meeting held on February 15 th, Dr. R. H. 

 Traquair gave some very interesting notes on carboni- 

 ferous Selachii found in clay beds under ironstone. He 

 also showed the meeting a remarkable fossil of a small 

 fish found in the Eskdale Bed, which was in shape some- 

 what like an eel, but which from its construction could 

 be in no way related to it. He proposed to call the 

 fossil Clwiidrenchelys probleinaticiis. Mr. Hugh Miller 

 described the effects of the earthquake in the Riviera as 

 he observed them three days after the shock. He 

 showed that the earthquake travelled from west to east, 

 from the fact that most of the chimney-pots were tilted 

 west, and that the east end of the houses was in every 

 case more damaged than the west. Mr. B. N. Peach 

 read a paper on a ne>v Eurypterid found in the upper 



