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level) for examination, where they were found to burn correctly, and 

 as at that time no one suspected the real cause of the discrepance, it 

 was concluded there had been some error in the length of our pen- 

 dulum, and there for the time the matter rested. 



" But as I was satisfied, for many reasons, that it was not owing to 

 an error in the pendulum, I determined to keep the subject in mind, 

 and for the practice in the following year (1849) I caused to be 

 made an adjustable pendulum which beat seconds very correctly for 

 several minutes. This pendulum was daily compared with two or 

 more seconds' watches to make all safe, and, as our longest time of 

 flight did not exceed twenty seconds, no error could possibly arise 

 from this source. The result was that the fuses again burnt too 

 long at Bangalore, and were again found to burn correctly at 

 St. Thomas's Mount. 



" This was a mystery to all; but after the matte rhad cost me much 

 thought, it occurred to me that the cause was to be sought in the 

 difference of altitude between St. Thomas's Mount and Bangalore, 

 nearly 3000 feet ; and as a means of putting this to the test, 1 sug- 

 gested that some fuses should be burnt at the Mount, or at Madras, 

 under a receiver, exhausted until the barometer stood at the Banga- 

 lore mean height, or about 27 inches. This, however, it was not 

 found convenient to do ; but, as an equally satisfactory way of test- 

 ing the accuracy of my conclusions, a small number of fuses were 

 prepared and burnt at St. Thomas's Mount, at Bangalore, and at 

 two different altitudes on the Neilgherry Hills, as will be seen by 

 the annexed copy of an official memorandum ; and although this ex- 

 periment was too limited to enable us to compile a scale of the pro- 

 bable times a certain length of fuse composition would burn at given 

 altitudes, it amply proves the fact that combustion is retarded at 

 considerable elevations. 



" Memorandum of an experiment to ascertain whether the atmo- 

 sphere influences the burning of fuses : 



" Eighteen 8-inch fuses, made of the same description of wood 

 (Congo), were filled with composition made for the purpose. The 

 same man drove the whole on the morning of the 2nd August 1849, 

 using the same mallet and drifts. Six of the fuses were burnt at the 

 Mount, six at Bangalore, and six on the Neilgherry Hills ; ail in the 

 presence of artillery officers ; the result is shown below " : 



