150 Scientific Intelligence. 



means of 1*5 grams fulminate in one end of the tube. In the first 

 trial the tube used was 14*46 meters long between the interrup- 

 ters, the first of these being placed 4 cm. behind the detonator, 

 and the second 4 cm. from the other end. The time required for 

 the wave to travel through the tube was 0-013980 second ; which 

 gives 1034 , 4 meters as the velocity of the explosive wave. In a 

 second trial, in which the tube was 11*77 meters long, the time 

 was 0*011491 second; giving a velocity of 1024*3 meters. The 

 results show that the velocity is affected by the compactness of 

 the charge, the size of the tube and even by the material of which 

 it is made. With ordinary gun-cotton for example, experiments 

 made in 1884 show that in lead tubes 4 mm. external diameter, 

 the density of the charge being from 1 to 1/2, the mean velocity 

 for lengths of 100 meters varied from 4952 to 5500 meters per 

 second, and for successive intervals of 25 meters, from 4671 to 

 5980 meters per second. In tubes of tin, the density of charge 

 being 1*2, the velocity was from 5736 to 6136 meters per second 

 in tubes 4 mm. external diameter, and 5845 to 6672 meters for 

 those of 5*5 mm. diameter. For gun cotton from hydrocellulose, 

 the mean velocity in tin tubes of 4 mm. diameter was 5916 meters, 

 and in those of 5*5 mm. 6100 meters; the velocity in lead tubes 

 4 mm. diameter being 5200 meters. With granulated gun cotton 

 densely charged, 1*17, in a 4 mm. tube, a velocity of 4770 meters 

 was obtained. In lead tubes 5*5 mm. external diameter, the 

 density of the charge being 1*27, the mean velocity was 5406 

 meters. With a less density of charge, 0*67 to 0-73, in lead tubes 

 8*44 to 10*6 mm. external diameter, the mean velocity varied from 

 3767 to 3795 meters. With nitro-starch, in a tin tube 4 mm. diam- 

 eter, the density being 1*2, the velocity varied from 5222 to 5674 

 meters, and in a tube 5*5 mm. 5816 meters. In a lead tube of 4 

 mm. the density being from 1*1 to 1*2, the velocity varied from 

 4886 to 5006 meters; rising to 5512 when the density was in- 

 creased to 1*35. Nitromannite with a density of 1*5 gave a veloc- 

 ity of 6965 meters; with a density of 1*9, of 7705. Nitroglycer- 

 in could not be made to detonate in lead tubes smaller than 3 mm. 

 internal diameter, unless the temperature was above 14°. Tubes 

 of this size placed in the sun gave velocities of 1310, 1015 and 

 1286 meters. Dynamite in Britannia tubes 3 mm. internal diame- 

 ter, gave a velocity of 2333 to 2753 meters. In lead or Britannia 

 tubes 6 mm. interior diameter from J 916 to 3180 meters; the 

 mean of all being 2668 meters. Panclastite (equal volumes of 

 petroleum of gravity 0*710 and hyponitric acid) in a tube of tin 5 

 mm. in diameter and 25 meters long, gave unsatisfactory results. 

 By using equal volumes carbon disulphide and hyponitric acid, 

 in a lead tube 3 mm. in diameter, a velocity of 4685 meters was 

 obtained in one experiment and 6658 meters in another. — Ann. 

 Chim. Phys., VI, vi, 556, Dec. 1885. G. f. b. 



3. On the Visible representation of the Ultra-red Rays. — In the 

 well known experiments of Tyndall on Calorescence, the focus of 

 the ultra-red rays, obtained by means of an absorption cell filled 



