240 GEOLOGICAL SURVEY IN SCOTLAND CHAP, vn 



near that coaly deposit that the Microlestes or Triassic mammifer was 

 found in a bone-bed, the exact circumstances of which I examined 

 last year, and will tell you about some day. 



Your O opposite the ' Upper Cretaceous ' is too often forgotten 

 when the progressive development advocates reason on the absence 

 of Upper Cretaceous mammalia. 



In regard to the Carboniferous delta, I would rather accept the 

 idea of many contemporaneous rivers debouching in one sea, than 

 suppose the coal-fields of the United States to have been all once 

 united, as H. D. Rogers supposes. Assuming these coal-fields to 

 be deltas, it is no doubt strange that we have so few terrestrial 

 fossils ; that it should have been left for me and Dawson to discover 

 the first land shell, and in America the first reptilian bones. Land 

 snakes may have existed on the then continents, even without 

 offending against the laws of progressive development, but when we 

 find them, and helices, and other signs of land creatures, the time 

 will come for speculating on the absence of higher vertebrata. 



The four O, O, O, O, or cyphers, opposite the four lowest 

 Palaeozoic groups, are significant. It was also well to insist on the 

 numerous subdivisions of the Oolitic period, and of others, each 

 separately equal to the ' Glacial and recent epochs.' 



If I did not take for granted that the condensed essay on the 

 glacial phenomena of Wales and other parts of the world was 

 to appear even more full and expanded in your ' Survey Memoirs,' I 

 should grudge its being given in an anonymous shape to any scientific 

 journal. The distinctness of the molluscan fauna on the opposite 

 shores of the Isthmus of Panama is well adverted to, and I suspect 

 unanswerable. Notwithstanding the upraised marine deposits in the 

 N. Polar regions, there is much low land, and so much sea, that 

 we have only to suppose a few such peaks as now lift themselves 

 up in the Antarctic regions (Mount Erebus, etc.), and I believe we 

 have the required cold. 



The quantity of reading and original observation adduced, 

 quite naturally and without parade, in the last eight or nine pages, 

 is prodigious, and not more than one in a hundred of the readers of 

 the Mag. will know how to appreciate. The few will do justice to it. 

 I am glad you paid a passing tribute to the ' illustrious ' one who 

 boldly led the way against the ridicule and scepticism of the ordinary 

 crowd in regard to Welsh glaciers. 



I am rather afraid, I confess, of D. Sharpe's paper, although in 

 the Elements I led the way before Murchison in transporting Alpine 

 blocks to the Jura by floating ice. But D. S. requires twice the 

 upheaval that I asked for as having occurred since the Glacial 

 Period. To raise mountains 9000 feet has probably required more 

 than a part of one geological period, and Studer and others have in 

 vain looked for marine shells in the Swiss drift. Fresh -water 



