CHAP. xii. THE GLACIAL THEORY. 1C5 



of the boulder clay as if it was a lover he was lingering 

 for. He went still higher up the river that day to 

 Dale House crossing the river from time to time, 

 startling the wild ducks, and inspecting the boulder clay 

 in all its windings. 



Dick found fourteen shells of the existing races which 

 he had extracted from the boulder clay, and he had no 

 doubt that this number might have been doubled. He 

 says " A list of these shells is necessary, not only to 

 mark my present success, but also to stimulate me to 

 further efforts." He accordingly subjoined a list of the 

 shells he had found, and sent it to Hugh Miller. " Thin 

 shell valves," he said, " such as Tellina, have been found 

 entire. Pieces of Cyprina are by far the most abundant. 

 But I suspect that it will not do to say that it was 

 owing to their superior strength their strong construc- 

 tion that they are found so very abundant. Mactra 

 and Tellina have received slight damage ; small young 

 Crassina (a month old ?) have withstood the fearful 

 shock of mountain waves, of dashing icebergs grinding 

 and pounding, whirling about and reeling like playthings 

 seas charged with mud, and stones of stupendous 

 weight ; all these have been tossing hither and thither, 

 ebbing and flowing, and the earth reeling ; and yet, a 

 diminutive little thing like this now lying before me has 

 been preserved! Amazing! I have met with many 

 stones in the boulder clay grooved and scratched and 

 rubbed in the strangest way imaginable. For the pre- 

 sence of these stones where they now are, I think the 

 glacial theory is the most likely. 



