MECHANICS AND USEFUL ARTS. 107 



phere renders it safe in making, storage, and transportation ; it 

 gives very little smoke, and very little residuum, and its strength 

 is not diminished by wet or a damp air; bein,g redried it contains 

 the same destructive power as it possessed originally ; and its 

 commercial value is said to be much less than that of any other 

 powder. 



In English war powder there are 75 parts of nitre, 10 of sul- 

 phur, and 15 of charcoal ; and for sporting powder 77 of nitre, 9 

 sulphur, and 14 of charcoal ; Neumeyer's powder consists of 75 

 parts of nitre, 6.25 of sulphur, and 18.75 of charcoal. To prepare 

 the charcoal, pieces of birch wood are ignited and placed in a re- 

 ceiver, which is hermetically closed. The charcoal thus obtained 

 is then soaked in soda-lye, and dried upon canvas strainers. It is 

 then reduced to a powder, and is incorporated in a moist state 

 with the other ingredients in the above proportions; it is then 

 converted into powder of any degree of fineness in the ordinary 

 way. 



The glazing is omitted, by which the tendency to absorb moist- 

 ure is said to be decreased. Its immunity from explosion whc-u 

 not inclosed was proved at the Sydenham Crystal Palace grounds, 

 where 2 kegs, containing 35 Ibs. of this powder, were ignited in 

 a small building ; each keg had a hole 5 inches in diameter in the 

 top, and the powder burned away without any explosion. 



* THE CHALMERS TARGET. 



This celebrated target, which seems to have resisted all shot 

 which the best English ordnance can send against it, consists 

 of wrought-iron hammered armor plates, 3| inches thick, behind 

 which is a backing of alternate layers of hard-wood timber and 

 iron plates, all strongly bolted together; in the rear of this back- 

 ing is another armor plate 1| inches thick; then a cushion of 

 timber 3| inches thick between it and a three-quarter inch plate, 

 representing the side of the ship. The whole of this compound 

 frame is held together by 2-inch screw bolts, with shallow 

 square threads. It seems to have resisted well the Palliser shot; 

 it remains to be seen how it will resist the 15-inch ball of the 

 American cast-iron smooth-bore cannon, the weight of the ball 

 being 453 pounds, the charge 100 pounds American mammoth grain 

 powder or 83 pounds English powder, with a velocity of 1,500 feet 

 per second. Some experiments as to the strength of targets were 

 recently made at Vincennes, when the 9-inch 12-ton Armstrong 

 gun failed to penetrate a 5^-inch plate of soft iron, backed on 

 the Chalmers system. Half a dozen rounds were fired at 25 yards' 

 distance, and at the close of the experiments it was found that 3 

 of the shot were lying in front of the target, and 3 sticking 

 in the backing. The full service charge of 43 pounds of powder 

 was employed, and the steel shot had the ogival head recom- 

 mended by Major Palliser. Recently the 7-inch Armstrong, with 

 a 15-pound charge, sent the Paliiser shot through plates 7 inches 

 thick at Shoeburyness. The plates were without backing, and 



