i88o.] 
On Water and A ir . 
259 
it comes down as snow. The snow becomes compared 
together as glaciers, and the whole process is due to the 
action of heat. Let me try to impress this thing upon 
your minds still more fully. Take the case of a great gla- 
cier near which, I am happy to say, I live for six or eight 
weeks every year — the great Aletch glacier. I look down 
upon that mass, all frozen as it is, forming a great river of 
ice, and I ask myself, What amount of solar heat has been 
necessary to produce that glacier ? Understand me W^hat 
amount of solar heat has been necessary to evaporate the water 
of the ocean so as to produce this glacier ? This amount 
of heat. Suppose a mass of iron five times the weight 
of that Aletch glacier. Suppose the mass of the glacier 
quintupled— rendered five times heavier than it is : suppose 
that mass of iron raised to the fusing-point of cast-iron 
white hot. The amount of solar heat which was necessary 
to produce the present Aletch glacier would be exactly equal 
to that which would be competent to raise to its fusing-point 
a mass of iron five times the weight of the glacier— compe- 
tent to raise the iron to a white heat. Hence you see here 
what a power the sun exerts in the produftion of those 
Alpine glaciers. In point of fadt, those who have speculated 
upon this subject forgot altogether that the case was one of 
distillation. We had a case of distillation here in our last 
ledture. I had some salt water boiled, and we condensed 
the steam from the saltwater in another vessel, thus pro- 
ducing sweet water : and that is precisely what is done by 
the distillation of the ocean. The ocean sends up its 
aqueous vapour into the air — sweet vapour without any salt. 
This vapour is again condensed and congealed in the higher 
regions of the atmosphere, and the process, as I have said, 
is one of natural distillation. In distillation heat is just as 
important as cold. You must have the heat to produce the 
vapour : you must have the cold to aft as a condenser. And 
this is the adtion of the mountains of Switzerland upon the 
aqueous vapour of the air. 
Observe here this beautiful flask covered with a white 
coating, which is due to the coagulation of the aqueous 
vapour of the breath that has come from your lungs. You 
have been breathing out into this atmosphere and rendering 
the atmosphere humid. I put a very cold mixture into that 
flask, and the vapour which came from your lungs has be- 
come congealed into hoar-frost on the surface of the flask. 
And I want to show you that the luminous rays of our 
domestic sun have no power whatever to melt the hoar- 
^ost. And so it is with regard to The glaciers of the Alps. 
