e of this nature was not possessed by the
distinguished writer just mentioned. The extension of Swiss glaciers
far beyond their present limits, was first made known by a Swiss
engineer named Venetz, who established, by the marks they had left
behind them, their former existence in places which they had long
forsaken. The subject of glacier extension was subsequently followed
up with distinguished success by Charpentier, Studer, and others. With
characteristic vigour Agassiz grappled with it, extending his
observations far beyond the domain of Switzerland. He came to this
country in 1840, and found in various places indubitable marks of
ancient glacier action. England, Scotland, Wales, and Ireland he
proved to have once given birth to glaciers. He visited Glen Roy,
surveyed the surrounding neighbourhood, and pronounced, as a
consequence of his investigation, the barriers which stopped the glens
and produced the parallel roads to have been barriers of ice. To Mr.
Jamieson, above all others, we are indebted for the thorough testing
and confirmation of this theory.

And let me here say that Agassiz is only too likely to be misrated and
misjudged by those who, though accurate within a limited sphere, fail
to grasp in their totality the motive powers invoked in scientific
investigation. True he lacked mechanical precision, but he abounded
in that force and freshness of the scientific imagination which in
some sciences, and probably in some stages of all sciences, are
essential to the creator of knowledge. To Agassiz was given, not the
art of the refiner, but the instinct of the discoverer, and the
strength of the delver who brings ore from the recesses of the mine.
That ore may contain its share of dross, but it also contains the
precious metal which gives employment to the refiner, and without
which his occupation would depart.

Let us dwell for a moment upon this subject of ancient glaciers. Under
a flask containing water, in which a thermometer is immersed, is
placed a Bunsen's lamp. The water is heated, reaches a temperature of
212 deg., and then begins to boil. The rise of the thermometer then
ceases, although heat continues to be poured by the lamp into the
water. What becomes of that heat? We know that it is consumed in the
molecular work of vaporization. In the experiment here arranged, the
steam passes from the flask through a tube into a second vessel kept
at a low temperature. Here it is condensed,