212 The Rocky Mountain Locust. 



whether of bird or insect, is, I conceive, easier, coeteris 

 paribus, in a dense than in an attenuated atmosphere. 



7. As the Rocky Mountain Locust multiplies continu- 

 ously in the Rocky Mountain region, its descent into the 

 plains to the east where it can not permanently thrive, 

 can not well be affected by the burning of the grass on those 

 plains. 



From what has preceded I think we may safely conclude 

 that the non-burning of the prairies will have no effect in 

 preventing locust injuries, but that, on the contrary, as 

 shown in Chapter VIII, the judicious burning of such 

 prairies at the proper time is most beneficial and highly to 

 be commended. 



Indeed, there is only one way in which there can be any 

 real connection between the burning of prairies and the 

 ravages of the Rocky Mountain Locust, and that connec- 

 tion is through the remote past, and altogether beyond our 

 present controL In the report of the Chief Signal Officer 

 to the War Department for 1872, will be found an inter- 

 esting account of the great fires of 1871 in the North- 

 west, in which the late Prof. J. A. Lapham, of Milwaukee, 

 Wis., maintains that our extensive Western prairies and 

 plains owe their existence and origin to the agency of fire. 

 These fires, encouraged by drouth, and either kindled by 

 accident or intention, have swept over the country for 

 ages, and while they leave the roots of the grass uninjured, 

 they destroy the germs of most other plants, including 

 forest trees; and Mr. Lapham pictures to himself a long- 

 past struggle between forest and prairie, in which the 

 latter, by the assistance of the Fire King, has gained and 

 held the vantage ground. 



While I do not agree with Prof. Lapham that the 

 remote cause of our prairies can be attributed to fire, yet 

 no one can doubt its agency at the present time in main- 



