Page:Popular Science Monthly Volume 3.djvu/767

Rh "These observations were also followed up in subsequent years, the results being recorded in a series of detached letters and essays of great interest. These were subsequently collected in a volume entitled 'Occasional Papers on the Theory of Glaciers,' published in 1859. The labors of Agassiz and Forbes are the two chief sources of our knowledge of glacier phenomena."

It would be difficult for an unbiassedunbiased [sic] person to find in these words any semblance of a "charge" against Principal Forbes. His friends and relatives may be dissatisfied to see the name of M. Agassiz placed first in relation to the question of the quicker central flow of glaciers; but in giving it this position I was guided by the printed data which are open to any writer upon this subject.

I have checked this brief historic statement by consulting again the proper authorities, and this is the result: In 1841 Principal Forbes became the guest of M. Agassiz on the glacier of the Aar; and in a very able article, published some time subsequently in the Edinburgh Review, he speaks of "the noble ardor, the generous friendship, the unvarying good temper, the true hospitality" of his host. In order to explain the subsequent action of Principal Forbes, it is necessary to say that the kindly feeling implied in the foregoing words did not continue long to subsist between him and M. Agassiz. I am dealing, however, for the moment with scientific facts, not with personal differences; and, as a matter of indisputable fact, M. Agassiz did, in 1841, incur the labor of boring six holes in a straight line across the glacier of the Aar, of fixing in these holes a series of piles, and of measuring, in 1842, the distance through which the motion of the glacier had carried them. This measurement was made on July 20th; some results of it were communicated to the Academy of Science in Paris on August 1st, and they stand in the "Comptes Rendus" of the Academy as an unquestionable record, from which date can be taken.

But the friends quarrelled. Who was to blame I will not venture here to intimate; but the assumption that M. Agassiz was wholly in the wrong would, I am bound to say, be required to justify the subsequent conduct of Principal Forbes. He was, I gather from the Life, acquainted with the use of surveying instruments; and knowing roughly the annual rate of glacier-motion, he would also know that through the precision attainable with a theodolite, a single day's—probably a single hour's motion—especially in summer, must be discernible. With such knowledge in his possession, as early as June, 1842, and without deeming it necessary to give his host of the Aar any notice of his intention, Principal Forbes repaired to the Mer de Glace, made in the first instance a few rapid measurements at the Montanvert, and in a letter dated from Courmayeur, on July 4th, communicated them to the editor of the Edinburgh New Philosophical Journal.

He did not at that time give any numbers expressing the ratio of the side to the central motion of the glacier, but contented himself with announcing the result in these terms: "The central portion of