not the very strongest point, is the following. Speaking of the principle of plasticity, Prof. Forbes writes:
"Perhaps the following illustration will appear to the impartial reader almost a demonstration of this principle.… There is a glacier basin in the range of Mont Blanc called the Glacier du Talèfre. Its outline is correctly represented in the next figure, as well as the relative dimensions of the mouth or outlet by which it pours forth the mass of ice which it is annually unable to contain in its circuit. The breadth of the outlet is about seven hundred yards, while the greater diameter of the basin which it discharges is more than forty-two hundred yards, or at least six times greater. Can it for one moment be imagined that any degree of lubrication of the bed of this cake of ice could drag it through the strait in question, even if its adhesion to the soil were absolutely nothing? The thing is impossible; it speaks for itself."[1]
The observation here referred to as so convincing is precisely of that class upon which Rendu founded his theory; and there cannot be a reasonable doubt that the very fact here brought forward more or less influenced him. Still, while in the hands of Prof. Forbes it has the value here set forth, in those of Rendu the "ingenious speculations" founded upon it are not "worthy of confidence."
It is not, and never was, my design to charge Principal Forbes with conscious wrong; but, at the time here referred to, I believed him to be animated by a love of public recognition so eager, and an estimate of the value of his own work so exalted, as to render it difficult for him to behave in a generous way toward those whose labors trenched upon his own. I regarded his treatment of Agassiz as harsh, if not merciless. Considering all this, I do not think that the "Glaciers of the Alps," written in the midst of such contentions as I have indicated, can be justly deemed intemperate in tone. Its logic is sometimes stern;[2] but its statements are irrefutable. To its chapters, from page 269 onward, I would refer the reader for an answer to a good deal of the irrelevant bluster associated with this question.
I am blamed for saying that, if Rendu had added to his other qualifications those of a land-surveyor, he would now be deemed the "Prince of Glacialists." Can this be for a moment doubted? When we find him announcing, with a fullness and precision never surpassed, and not attained even by Prof. Forbes himself until years after the publication of his "Travels," the character of glacier-motion; when we find him laboriously trying to determine it by observations of blocks at the edge and toward the middle of the glacier—is it to be imagined that, if he knew the use of the theodolite, he would not have employed that instrument? And is the absence of this surveyor's knowledge a just reason for dismissing his labors in the fol-
