Correspondence — Mr. J. Durham. 287 



I think that had I seen Mr. Downes' specimen I should have separated 

 it under a distinct specific name instead of considering it merely 

 a variety. It is singular that Dr. Fitton included N. pectinata in his 

 list of Blackdown fossils ; but as no specimen was known, I thought 

 it likely that a specimen of N. antiquata, exhibiting pectinate struc- 

 ture, and which is still preserA'ed in his original collection at Bristol, 

 had been mistaken for it. I had previously noticed Blackdown 

 species in the Grey Chalk, and think that when allowance is made 

 for the different quality of sea-bottom, and the much gi-eater probable 

 depth of the Chalk sea, enough species will remain in common to 

 prove that the two formations are practically of about the same age, 

 or that at least the Blackdown Beds are much newer than the G-ault. 



J. Starkie Gardner. 



"ELEVATION AND SUBSIDENCE." 



Sir, — I either fail to comprehend Mr. Starkie Gardner's argument, 

 or he seems strangely to misunderstand the value of the evidence 

 afforded by the presence of stratified sand with marine shells at an 

 elevation of 500 feet in Scotland. He seems to admit that it 

 means the total disappearance of all ice below that level. Now this 

 implies that the larger proportion of the ice-sheet, which he assumes 

 was the cause of the depression of the land, had been entirely 

 removed, and further that a very considerable part of it must have 

 been floated off long before that degree of submergence was reached 

 — assuming with Mr. Gardner that the land was depressed during 

 glacial conditions, which is not the belief of the most competent 

 authorities upon the giaciation of Scotland. 



Mr. Gardner says that in the course of submergence "the Firth 

 of Tay would in fact become a fiord." I do not wish to repeat Mr. 

 Gardner's slighting phrase, but I really do not know wlat he 

 means by that. 1 understand that fiord and firth are convertible 

 terms, or perhaps that the latter is a fair attempt to spell out in 

 English the Norse pronunciation of the former word. But what the 

 Forth of Tay would actually become were the land depressed 500 

 feet would be part of a wide sea joining the North Sea to the 

 Atlantic, and stretching from the flanks of the Grampians to the 

 Southern Uplands, a sea certainly studded with innumerable islands, 

 but few if any of them of sufficient area to bear an ice- cap, and not 

 only would the great central valley of Scotland be turned into an 

 archipelago, while vast tracts all round the coast as well as the Great 

 Glen (through which the Caledonian Canal passes) would be deeply 

 submerged, but even the mountainous regions that remained would 

 be invaded in all directions by great firths occupying what are now 

 the highland glens. 



But apart from this sweeping removal of the ice, foot by foot, as 

 the land sank down, the load of ice would be proportionately 

 lightened, so that it would really be an instance of depression accom- 

 panied by unloading, not, as the new theory demands, depression 

 by loading, and in proportion to the amount of the loading. 



Mr. Gardiner writes somewhat contemptuously of the phrase 



