Sir

Mr Prestwich’s paper on the Parallel Roads of Lochaber seems to me a very valuable contribution to this long disputed subject, & I strongly recommend it to be printed in extenso in the Transactions; for although the abstract is remarkably clear, the full details are necessary for any final judgment & would be indispensable to any one hereafter revisiting the district.¹ There are also many valuable, incidental discussions on glacial action. It is to be regretted that the author does not explain how it was (considering the height of the surrounding mountains) that during the second glacial period the valleys were not swept clear of their detritus, including the parallel roads. With respect to illustrations, Map I is indispensable: Map II does not seem necessary, but only advantageous.² Of the wood-cuts Fig. 3 (viz a sketch of Glenroy) is hardly necessary, & perhaps two or three of the smaller diagrams might be omitted, but their cost would be trifling.³

Finally, I ought perhaps to caution the Council, that from having formerly attended to the Parallel Roads, I may over-estimate the interest of the present memoir.⁴ On the other hand every one will admit that so unique a phenomenon deserves the fullest consideration, standing as it does, in intimate connection with one of the most remarkable of all the epochs in the earth’s history, namely the Glacial Period.

I remain. Sir | Your obedient servant | Charles Darwin

To the Sec^y | R. Soc^y.

P.S. Paper despatched today by Rail