410 Capt. Noble and Mr. F. A. Abel [June 18, 



varied from over 36 tons on the square inch to about 1 ton on the square 

 inch. 



The dangerous nature of the operations of explosion, carried out on so 

 considerable a scale as in these investigations, rendered great precautions 

 necessary. Unless the explosion-cylinder was most perfectly closed, the 

 violent escape of gas resulted in its immediately cutting a way out for itself, 

 destroying the arrangement for closing the apparatus. 



Special observaiaons were made to ascertain how long a period elapsed 

 after explosion before the non-gaseous products assumed the solid form. 

 They appeared to do this a little within two minutes after explosion, when 

 a charge nearly filling the vessel was used. 



The method employed for collecting the gaseous products as soon as 

 possible after the explosion presented no special feature of novelty. On 

 opening the explosion-vessel after the gases had been allowed to escape, 

 the solid products were found collected at the bottom, there being gene- 

 rally an exceedingly thin (in fact, with large charges, quite an inappreciable) 

 deposit on the sides. The surface of the deposit was generally perfectly 

 smooth and of a very dark grey, almost black, colour. This colour, how- 

 ever, was only superficial, and through the black could be perceived what 

 was probably the real colour of the surface, a dark olive-green. The sur- 

 face of the deposit, and the sides of the cylinders, had a somewhat greasy 

 appearance, and were indeed greasy to the touch. On the smooth surface 

 were frequently observed very minute particles, in appearance like soot, 

 but of the greasy texture to which allusion has been made. 



The removal of the deposit was generally attended with great difficulty, 

 as it formed an exceedingly hard and compact mass, which always had to 

 be cut out with steel chisels. Lumps would frequently break off, but a 

 considerable portion flew off before the chisel in fine dust. In various 

 experiments, on examining the fracture as exhibited by the lumps, the 

 variation in physical appearance was very striking, there being marked 

 differences in colour, and also, frequently, a marked absence of homo- 

 geneity, patches of different colours being interspersed with the more 

 uniform shade of the fracture. There was no appearance of general crys- 

 talline structure in the deposit ; but, on examination with a microscope, 

 and sometimes with the naked eye, shining crystals of metallic lustre 

 (sulphide of iron) were observed. On the whole, the general appearance 

 of the deposit was attended with such considerable variations, that, for 

 minute details, reference must be made to the account of the experiments 

 themselves. The deposit always smelt powerfully of sulphuretted hy- 

 drogen, and, frequently, strongly of ammonia. It was always exceedingly 

 deliquescent, and after a short exposure to the air became black on the 

 surface, gradually passing over into an inky-looking pasty mass. As in 

 physical appearance, so in behaviour, when removed from the cylinder, 

 there were considerable differences between the experiments. The de- 

 posit was transferred to thoroughly dried and warm bottles, and sealed 



