PRESIDENTIAL ADDRESS. 133 
awith the elements of water into its substance, restoring to 
the atmosphere in a free condition the oxygen that the 
animal had combined. Truly a beautiful natural adaptation 
that cails for our admiration afresh whenever it is presented 
to us! 
The organic matter in the soil and in the plant comes from 
the air, and the organic matter of the animal comes from the 
plant. So that, except the little morganic matter they 
contain, the substance of the vegetable and animal worlds 
come out of the atmosphere. They are buiit out of air 
We find, then, all this never-ending traffic in the con- 
stituents of the atmosphere, from the air to the waters on 
the earth’s surface, and to the waters under the earth, carried 
through the strata and thesolid rocks, and performing known 
and unknown chemical changes with often long and compli- 
cated geological careers, returning in part to the upper world 
again in the springs (argon and helium carbon dioxide and 
the rest), and by way of volcanoes of fire and mud; and, in 
the outward breath of the earth, into and out of the seas and 
lakes and streams, into and out of the bodies of plant and 
animal, in the land and in the waters, and throughout the 
atmosphere, with diffusive interchange, and by the mechani- 
cal movements of the winds. If we are to accept recently- 
revived suggested possibilities, this traffic may not be con- 
fined to the liquid and solid earth and its gaseous envelope, 
but have to include an exchange of atmospheric gases with 
systems across intersiellar spaces. 
Work AWAITING WORKERS. 
I have referred thus in bold, and necessarily imperfect. 
outline to the traffic in air and its constituents, with the 
object of drawing attention to some of the questions that 
still await investigation; and I have referred to the de 
termination of only a few of the substances that are usually 
found in normal air; but it would seem that, just as we may 
regard the sea as the world in solution, so may we, with 
perhaps equal truth, consider atmospheric air not simply as 
what has been left over from the making of the earth up 
to the present moment, but as the earth in a gaseous con- 
dition, with, especially in the lower regions, solids and liquids 
in molecular condition, or in fine suspension; and just as 
we almost seem to be able co find any element in the sea 
for which we seek diligently enough, so, possibly, for the 
atmosphere. We can see how much yet remains to be done. 
It is of great importance, in the first place, that old experi- 
