PRESIDENPIAL ADDRESS. 115 
thought our very thoughts. Indeed, we may regard these 
‘men not as ancients, but as virtually our contemporaries. 
We are storming ‘the self-same citadels at this time that 
these men stormed. 
Tf the solution of these problems are forever heane us, 
as some delight to tell us—at an infinite distance from us— 
then we can be no nearer them now, with all our science, 
than were our ancestors before us. But, although we may 
be looking out upon the same world that is always fresh and 
young, with its yearly miracle of the spring, and its round 
of seasons, and canopied by the same universe of stars, we 
regard the problems presented to us from a very different 
standpoint. We have made so many of the thoughts that 
nature embodies, our own. Just as “the greater the light 
the greater the circle of surrounding darkness,’’ so the 
splendid scientific triumphs of the last century, whilst en- 
larging our circle of light, have left us truly with an 
enormously extended horizon of the unknown. 
And, happily, it must increase. It is the ideal condition 
for the scientific man, for who would envy a scientific 
Alexander, possessed of the whole knowledge of the unt 
verse—a universe of knowledge—and with nothing left to 
investigate. 
We have now to pass to the introduction to modern 
science, so as to find what information an appeal to experi- 
ment has broughti us with respect to the composition of 
atmospheric air. 
EXPERIMENTAL RESEARCH ENDING IN DISCOVERY. 
Van Helmont (1577-1644) seems to have been the first to 
use the term gas, and to point out the existence’ of more than 
one kind of air. He distinguished “ gas sylvestre’”’ (car- 
bonic acid gas) from common air, and recognised it as the 
deadly gas of the Grotto del Cane, and that the same gas 
resulted from combustion, and was the product of putrefac- 
tion. In addition to this, he makes note of an inflammable 
gas, the result of the natural decomposition of waste animal 
substance, and which he called ‘“‘ gas pinque.”’ But these im- 
portant discoveries found no sympathy and awakened no in- 
terest, as far as we know, because they were mere by-pro- 
ducts of his search for a universal medicine. It was reserved 
for Black (1728-1799) to fiz this air, and demonstrate its 
nature by the use of the balance in a research that will be 
for ever memorable. In the meantime, all these observa 
tions of Van Helmont lay buried and forgotten; but a new 
era was close at hand, an era in which all these questions 
