T. F. Jamieson — Changes of Level in Glacial Period. 489 



The first thing that led me to suspect how the matter stood was 

 'the discovery of the older beds on the west coast, and the mode in 

 which they generally presented themselves, for I then began to see 

 that these were the true equivalents of our east coast ones, and that 

 the reason of the great difference between them and the later Clyde 

 beds was mainly that the latter had never been exposed to the same 

 treatment. They had escaped the destructive action of the last 

 glaciation and belonged to a newer stage. Hence the better 

 preservation of the beds, the greater abundance of the fossils, and 

 the more perfect state in which the shells are found. 



The red clay in which Arctic shells (generally broken) have been 

 got at Belhelvie and other places on the Aberdeenshire coast, can be 

 ^hown to be of earlier date than the last glaciation, seeing that it is 

 covered by the gravelly moraines of the last stream of ice which 

 came down to the coast along the valleys of the Dee and Don. 

 Agassiz, who visited these gravel hills along with Dr. Fleming in 

 184:0, was confident they were moraines, while Fleming was equally 

 satisfied that their formation was posterior to the shell-bearing clay 

 beside them, seeing that they not only lie above the clay, but also 

 occasionally contain rolled masses of it (see "Lithology of Edinburgh," 

 p. 82), all which I can confirm. This reddish clay of the east 

 midland coast of Scotland contains not only Arctic shells occasionally, 

 but also bits of chalk, which are sometimes well scratched- and 

 rubbed as if by ice. These chalk fragments were probably brought 

 to our shores by the Scandinavian ice which passed over and 

 destroyed some of the Danish chalk. They are by no means un- 

 common at Belhelvie and Montrose, and occur also at Barry, 

 Portobello, and Peterhead. There is, therefore, some reason to 

 believe that all these clays of the east midland coast of Scotland 

 which contain Arctic shells and bits of chalk belong to approximately 

 -one and the same period — a period previous to the last general 

 -glaciation, and consequently earlier than the later Clyde beds, with 

 which they should not be confounded. 



Now if I am right as to the absence of the later Arctic shell-beds 

 on the east side of Scotland, how are we to account for it ? It 

 iSeems to me that it might be simply the result of the unequal 

 pressure of ice on the two sides of the kingdom, the heavy load on 

 the went causing a depression and submergence which ditl not affect 

 the east side. Indeed, the tendency there would rather be to a rise 

 owing to the reason previously mentioned. 



In my paper on the Parallel Eoads of Glen Koy in 1863, I drew 

 particular attention to the evidence of extreme glaciation along the 

 west coast, and I suggested that as the rainfall there far exceeds 

 that of the east, so in former times the fall of snow would be in like 

 excess, hence heavier ice would result. The rainfall along the west 

 of Scotland is two or three times what it is on the east, while on 

 the mountains the excess is far greater. The annual average 

 measured by the rain-gauge on the top of Ben Nevis for the nineteen 

 years ending 1903 is no less than 160 inches, while at Fort William, 

 close to the bottom of the hill, it is not more than 78 inches, or just 



