RATS. 43 



tain. The ibnrier I am inclhied to believe to be 

 the case in this state, but of this I am not certain. 

 The waters of these western streams have a self- 

 puddling power. They are saturated with lime, 

 gj^psum, and vegetable and mineral decomposi- 

 tions, and their depositions will gradually fill up 

 the leaks and fissures in the canal. You know 

 that a canal has been cuttlirough the bog of Allan 

 in Ireland at an immense expense, and which is 

 perfecdy water "tight. The comparative facilit}^ 

 of making the western canal in the worst places is 

 obvious. The freshets of spring and autumn — 

 the heavy rains and snows of winter — and the 

 operations of fro^t, have exhausted, the last season, 

 all their powers^against this communication, and 

 it has stood the shock at a trifling expense. In 

 some places there is quick sand, which ever shift- 

 ing and sliding, requires strong protection against 

 its ravages. 



1 presume you know that moles and rats are so 

 injurious to canals in England, that rat catchers 

 are employed to extirpnte them. I have seen 

 already in some places the holes of these animals ; 

 I do not know whether the brown, gray, or Nor- 

 way rat, the mus decumanus of LinuEcus and nius 

 ?\lvestris of Pennant, or the black rat, mus rattus 

 ofLinucCUS, have e vtended thuir migraiions as far 

 as this part of the country. They both follow 



