480 Canadian Record of Science. 



so long ago that I can only recollect their general purport. 

 According to his report, one season before, I think that of 

 1813, and perhaps also the one previous, had been extremely 

 favourable for the production of mast. Wild fruit and nuts 

 were in unusual abundance. Then winter set in with a 

 fall of snow which covered the ground before it was frozen, 

 and it remained so covered the whole season. In the 

 woods, therefore, in such circumstances and with such 

 abundance of food, the mice would multiply rapidly. 

 During the summer of 1814,. as Mr. Graham says, they 

 began to show themselves, but still they had sufficient food 

 in the forest. That summer, however, did not prove so 

 favourable, so that, with their increased numbers and 

 decreased supply of food, by the spring of 1815 the woods 

 no longer afforded them the means of subsistence, and they 

 were driven to seek it in the clearings. The same cause, 

 namely, " a failure of their ordinary food in the woods," is 

 assigned by Sir W. Dawson, in the paper referred to above. 

 I cannot but think, however, that if, on the one hand, there 

 were such circumstances favourable to their multiplication, 

 on the other, the destruction which had been going on among 

 the fur-bearing animals for some time, must have been re- 

 moving one of the natural barriers to their increase, and thus 

 helped to produce the result. 



At all events, when we consider the fecundity of these 

 creatures, that they produce from five to eight young at a 

 birth, and this at intervals of from one to two months, so 

 that it has baen calculated that a single pair might in one 

 year produce 20,000, we need not be surprised that under 

 circumstances favourable for their increase, and with the 

 removal, in any measure, of the checks which Nature has 

 set up against it, they should on occasions appear in such 

 overwhelming numbers. 



Other bearings of the subject I must leave to skilled 

 naturalists to consider. 



