MEMOIR OF THE LATE DR. HENRY. 115 
various papers communicated to the society and 
printed in the Philosophical Transactions. 
The same analytical method by which the 
decomposition of muriatic acid gas had been 
effectuated was in 1809 employed by Dr. Henry 
to resolve ammonia into its constituent gases. 
These experiments may even now be commended 
as models of extreme accuracy. Ammoniacal 
gas previously dried with great care, was found 
to expand to double its primitive volume after 
a sufficient number of electrical discharges. 
The average of eight experiments (in five of 
which the volume was exactly doubled) gave 
the relation of 100:198.78 between the volumes 
of gas before and after decomposition, a con- 
formity between theory and experiment, which 
modern refinement cannot surpass. In this 
memoir Dr. Henry also made known a remarka- 
bly elegant and expeditious method of analysing 
ammonia, by firing it in a volta tube with a 
deficient quantity of oxygen. In this process 
all the ammonia is decomposed, though a part 
only of the hydrogen thus liberated meets with 
its equivalent of oxygen. More oxygen is then 
added to burn the residuary hydrogen :—for Dr. 
Henry had observed, that if the whole quantity 
of oxygen was added at once, the results were 
