376 SNAKES. 



gradually expel these latter.' When lost by accident or 

 by violence, therefore, the process of replacement is slower, 

 as we can readily conceive, the ' secondary ' next in turn not 

 being as yet ready for duty. 



Though the American scientific journals devoted to zoology 

 are rich in ophidian literature, there are few available to 

 English students ; and I regret I am unable to ascertain 

 from across the Atlantic the latest researches and conclusions 

 regarding this and several other correlative points. To 

 Professor Martin Duncan I am indebted for the loan of 

 a volume which forms one of the ' Bulletins ' of the United 

 States Geological Surveys, containing a valuable 'Report' on 

 the Crotalus by Dr. Elliot Coues, of the United States army, 

 late surgeon and naturalist to the United States Northern 

 Boundary Commission, 1878. 



It is these frequent Exploring Expeditions of America 

 that have done so much to enrich science in all its branches ; 

 as to them are appointed efficient geologists, botanists, 

 naturalists, and other scientists, who send in their ' Reports ' 

 to Government, to be soon reproduced in the form of large, 

 handsomely-illustrated volumes. Copies of these (often 

 consisting of ten to eighteen thick quartos) are presented 

 to the members of Congress, governors of States, and to 

 many others in office, also to literary institutions. You may 

 have access to them in almost every large town in America ; 

 and there is no information connected with the history and 

 natural productions of the nation (including the aborigines) 

 that cannot be found in their pages. And as our Trans- 

 atlantic cousins are always exploring some new territory, 

 and have still untold square miles of mountain and valley 



