THE GLACIERS AND THEIR INVESTIGATORS. 749 



" 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 unbiassed 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 dif- 

 ferences ; 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 sub- 

 sequent 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 dis- 

 cernible. 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, com- 

 municated 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 



