367 



author's experiments with six-inch or thirty-seconds fuses burnt in 

 artificially rarefied air are embodied in the following table : 



There are here evident indications of the rate of retardation being 

 somewhat greater at low than at comparatively high pressures ; but, 

 neglecting these indications, the above numbers give 1*043 second 

 as the average retardation in a six-inch or thirty-seconds fuse for 

 each inch of mercurial pressure removed. This result agrees closely 

 with that obtained by Quartermaster Mitchell, if we except those 

 fuses which he burnt at the greatest altitude ; and in reference to 

 which some error must obviously have crept in. The following 

 table shows Mr. Mitchell's results uniformly with those in the last 

 table. The fuses which he employed were fifteen-seconds or three- 

 inch ones, and their times of combustion have therefore been multi- 

 plied by two in order to bring them into comparison with the six- 

 inch fuses which were used in the author's experiments : 



Here, omitting the last determination as abnormal, we have the 

 average retardation, in the combustion of a six-inch fuse, for each 



