Obituary — Dr. David Robertson. 95 



weeks of finishing his ninetieth year. It must not be fancied from 

 his age that his claim to be noticed in this Magazine depends on his 

 having become, as is sometimes the result of longevity, a breathing 

 fossil. On the contrary, his scientific activity vv^as maintained 

 unflinchingly to the end. He became a Fellow of the Geological 

 Society of London in 1869, but he had joined the Geological Society 

 of Glasgow two years earlier. To the Quartei'ly Journal of the 

 former he contributed but one short paper ; to the Transactions 

 of the latter a long series of Essays, many of them in collaboration 

 with the late Dr. Orosskey on post-Tertiary Clays. Together with 

 G. S. Brady and Orosskey, he compiled for the Palseontographical 

 Society an important Monograph on the post-Tertiary Entomostraca 

 of Scotland. 



In the words of Mr. Dugald Bell, Eobertson's work in geology 

 was distinctively that of a zoologist, but characterized, like all his 

 other work, by its minute and painstaking thoroughness. " He 

 seldom, if ever, meddled with questions of stratigraphical or physical 

 geology. In conversation he sometimes ' beat over ' certain points 

 in glacial geology, and his statement of doubts and difficulties here 

 and there was always very suggestive. But he alwaj's fell back 

 upon his labours to unfold the life of the period as far as possible, in 

 all its varieties, even the humblest. The principal observations of 

 a more general kind, relating to what may be called physical 

 matters, which I remember as coming from him, are (1) his note 

 on the accelerated precipitation of sediment in salt-water as com- 

 pared with fresh ; and (2) his remark that a lighter or browner 

 colour of the Upper Boulder-clay, as compared with the Lower, was 

 due very frequently at least, not to any difference in materials or in 

 conditions of deposition, but simply to the action of the weathering 

 agencies to a certain depth from the surface on the ferruginous 

 elements contained in the clay. These observations were wrought 

 out with great clearness, and have been very helpful in some 

 points." (Mr. Dugald Bell in litt.) 



From 1892 onwards Robertson was on a Oommittee of the British 

 Association for investigating certain shell-bearing clay deposits in 

 various parts of Scotland. When a man of eighty-six is placed on 

 such a committee, it might well be supposed to be done out of pure 

 compliment, or for the countenance of a distinguished name, or at 

 most to add the authority of an experienced judgment to the results 

 of younger men's labour in the field. A far diiferent view of the 

 responsibility^ was taken alike by those who selected Eobertson, and 

 by the man of their choice. Each year a substantial part of the 

 report has been from his pen. Each year a substantial part of 

 the work has been accomplished by his exertions. He undertook 

 the preparation of the samples of clay, and the determination of 

 the various organic remains, many of them extremely minute or 

 fragmentary, which resulted from the careful washing, straining, 

 and separating of the constituent gravel, sand, and mud. The 

 tediousness of the occupation none can know but those who have 

 tried it. In private correspondence Eobertson would speak of the 



