NATURAL PHILOSOPHY. 187 



upon tlie lamp, when the force of the gas is diminished. Other- 

 wise the proportion becomes such that an explosive mixture is 

 formed. For this reason it is more convenient to use an arrange- 

 ment in which the excess of air can be regulated by an exterior 

 tube sliding obliquely downward over the air-apertures. The 

 gas-jet should be on a level with the top of these apertures, which 

 must be much larger than those of the ordinary Bunsen 

 burner. 



Mr. Brown, of the War Office Chemical Department, has dis- 

 covered a remarkable property connected with the ignition and 

 explosion of gun-cotton. He has found that the explosive force 

 of gun-cotton may, like that of nitro-glycerine, be developed by 

 the exposure of thq substance to the sudden concussion produced 

 by a detonation ; and that, if exploded by that agency, the sud- 

 denness and consequent violence of its action greatly exceed that 

 of its explosion by means of a highly heated body or flame. It 

 follows, that gun-cotton, even when freely exposed to air, may be 

 made to explode with destructive violence, apparently not inferior 

 to that of nitro-glycerine, simply by employing for its explosion 

 a fuse to which is attached a small detonating charge. Some 

 remarkable results have been already obtained with this new 

 mode of exploding gun-cotton. Large blocks of granite, and 

 other very hard rock, and iron plates of some thickness, have 

 been shattered by exploding small charges of gun-cotton which 

 simply rested upon their upper surfaces. Further, long charges 

 or trains of gun-cotton, simply placed upon the ground against 

 stockades of great strength, and wholly unconfined, have been 

 exploded by means of detonating fuses placed in the centre or 

 at one end of the train, and produced uniformly destructive 

 effects throughout their entire length, the results corresponding 

 to those produced by 8 or 10 times the amount of gunpowder 

 when applied under the most favorable conditions. Mining and 

 quarrying operations, with gun-cotton applied in the new man- 

 ner, have furnished results quite equal to those obtained with 

 nitro-glycerine, and have proved conclusively that if gun-cotton 

 is exploded by detonation, it is unnecessary to confine the charge 

 in the blast-hole by the process of hard-tamping, as the explosion 

 of the entire charge takes place too suddenly for its efi"ects to be 

 appreciably diminished by the line of escape presented by the 

 blast-hole. Thus the most dangerous of all operations connected 

 with mining may be dispensed with when gun-cotton fired by the 

 new system is employed. — Quarterly Journal of Science ^ Aprils 

 1869. 



FACTS IN NATURAL PHILOSOPHY. 



Radiation of Heat from tlie Moon. — The Earl of Rosse is mak- 

 ing a series of experiments, by means of a thermo-pile of 4 ele- 

 ments and a S-foot telescope, to determine, if possible, what pro- 

 portion of the moon's h(?at consists of — 1. Tliat coming from the 

 interior of the moon, which will not vary with the phase; 2. 

 That which falls from the sun on the moon's surface, and is at 



