FRESH AIR. 9 
more than is absolutely necessary, the action of this beneficial 
agent on their system.* 
Let us now consider the variable constituents of our pure 
atmosphere. These are carbonic acid gas and the vapour of 
water. We have seen that carbonic acid is constantly being’ 
thrown into the atmosphere by the breathing of animals. 
There are several other natural sources of this agent. All the 
putrefaction and fermentation of animal and vegetable sub- 
stances is attended with the evolution of this gas. There is 
another natural source, and that is volcanic action, which is 
constantly supplying this gas. Of the gases which are thrown 
out from volcanoes, this is most abundant. It is one of those 
sources of carbon and oxygen to the surface of the earth 
which will account for a phenomenon not otherwise easily 
explained, and that is, the constant increase of organized 
beings on the surface of the earth. When Adam and Eve 
alone occupied the earth, about thirty-five pounds of carbon 
sufficed to organize the whole human race ; but now we have 
500,000,000 times that quantity in men and women alone. 
Add to these the domestic animals by which they are sur- 
rounded, it will be seen that the demands for carbon upon the 
atmosphere through the vegetable kingdom has been enor- 
mous, and has constantly increased. The never-failing* supply 
of this carbon is volcanic action. Thus, we see that the in- 
crease of man on the earth, and his hope of multiplying in 
ages to come, is dependent on that action which produces 
volcanoes and earthquakes. Thus it is that the very phenomena 
which have sometimes been regarded as proofs of the wrath of 
God in a fallen world are blessings, abounding with all possible 
goodness to the human race. 
These natural supplies of carbonic acid gas are supplemented 
by others produced by man himself. He consumes carbon for 
cooking, warming, and manufacturing purposes, and it has 
been calculated that a thousand millions of men consume 
yearly upwards of 2,000,000,000,000 of pounds of carbon. 
This quantity is again increased by artificial fermentation, by 
tobacco-smoking, by lime-burning, and other sources, to a 
prodigious extent, when we calculate the real quantity con- 
sumed. Yet, all this carbonic acid, were it allowed to accu- 
mulate, would form but a small quantity in the great aerial 
ocean by which we are surrounded. In the pure air of the 
Alps and of the sea it forms but about a fortieth per cent., by 
In some experiments made at Brighton, in 1862, I found in a room with 
the window open, that whilst ozone test-paper was readily coloured at the 
open window, it was not changed at all at the hack of the room, showing 
that the impurities of the atmosphere of a room with an open window were 
sufficient to destroy all the ozone that entered it. 
