HYDROGEN AND OXYGEN. 



95 



with rectilinear and horizontal leaden tube 42*45 metres long 1 

 and '005 of a metre in diameter. 



It was filled with an electrolytic mixture of hydrogen and 

 oxygen, under atmospheric pressure. After each experiment, 

 the tube was dried by causing 

 a current of dry air to circulate 

 through it for several hours. 



The following table gives all 

 the experiments. The extreme 

 results have not been eliminated 

 from it as is sometimes done. 



Mean 0-014860 2861-1 



The mean variation in one ex- 

 periment amounts to 79 metres, 

 the maximum variation to -f- 190 

 metres and - 186 metres, corre- 

 sponding to intervals of time 

 equal to + 0-00095, or at the 

 maximum nearly joW f a 

 second, the mean error being 

 half this quantity. With the 

 oxyhydrogen mixture, the mean 

 length measured on the rod of 

 the chronographs is equal to 

 0448 metre, which figures give 

 a clearer idea of the degree of 

 exactness attained in measure- 

 ments of this order. With the 

 mixture of carbonic oxide and 

 oxygen, this length amounted 

 to 107 metre. 



The mean error in the experi- 

 ments is ten times as great as 

 that recorded by the chrono- 

 graph. This arises, not from 

 the instrument itself, but from 

 the unequal delays occurring in 

 the process of interruption employed. It is known that such 

 1 All the lengths are taken between the two interruptions. 



Fig. 15. Le Boulenge Chronograph- 

 chronometer. 



