50 PRESIDENT’S ADDRESS. 
hydrogen also present in a great many different varieties of 
rocks, and in comparatively large proportions to the volume 
of other gases; no free oxygen was found, hence it may be 
that the hydrogen was originally present as water at a high 
temperature, and that the oxygen has been removed by 
metallic or other oxidisable substances. It may be that 
the nascent hydrogen combines in part with nitrogen to 
form ammonia, which would account for the presence of 
ammonia in minerals and igneous rocks. 
The presence of methane and other hydrocarbons, and of 
petroleum in rocks, is thought to show that in the lower part 
of the earth’s crust there exist metallic masses and com- 
pounds of metals with carbon; for such when in contact 
with water at a high temperature would give rise to metallic 
oxides, and to gaseous and liquid hydrocarbons, as sug- 
gested by Mendeléeff. This is also supported by Moissan’s 
recent researches on the metallic carbides, and we have the 
now familiar method of making an illuminating gas (acetylene) 
by adding water to one of them, viz., calcium carbide. 
There are many other matters of more or less general 
interest in chemistry which might have been touched upon, 
did time permit, such as the recent advances in our know- 
ledge of Solar and Stellar chemistry ; the occurrence and 
distribution of the rare elements, and especially of the rare 
metals, because so many of them are now entering into daily 
use—as in the case of other commodities the demand reacts 
upon the supply—e.g., substances like thoria, a few years 
ago only obtainable by the grain weight, are now produced 
by the ton ; also upon cellulose and the manufacture from it 
of the so-called artificial silk, but better termed imitation 
silk, as it is of a totally different composition to true silk. 
In conclusion, I sincerely trust that our non-resident 
members will have no cause to regret their visit to Sydney, 
in this the least pleasant part of the year, and that the 
Session will be a profitable one to all concerned, and 
especially that the work of the meeting will distinctly 
mark an advancement of science in Australasia. 
