840 TEAySACTIONS OF THE AMERICAN IXSTITUTS. 



ter months 45^. Until two years ag^o, rain Avas unknown, but in 

 twelve months, endinf^ in April last, there were actually fourteen 

 days on which rain fell, and lately there fell a tremendous shower of 

 rain — a phenomenon which the oldest Arab had never previously 

 witnessed. Rain ceases to fall on a country deprived of its forests, 

 or only falls in violent storms. Ilgre we see rain return in <^ to tho 

 desert on restoring the trees. 



This item caUed forth some discussion. 



Dr. Edwards. — This is probably due to the fact that plants evapo- 

 rate so much "water, and this water returns in the form of rain. 



Dr. Tillman. — And yet the ground under forests is invariably 

 damp. 



Mr. Phin. — It is not probable that the same water which is evapo- 

 rated by the plants will return to the soil from which it was taken. 

 The subject is one of great difficulty, and no theory that fully 

 accounts for the phenomena-has yet been propounded. It is not 

 improbable that the trees act as lightning rods, and that the influ- 

 ence exerted in this way causes the rain to be precipitated. 



Wells Dug by Praikie Dogs. 

 Mr. G. M. Sternberg, in the American JSTaturalist, raises the ques- 

 tion as to the manner in which the prairie dpg obtains its supply of 

 M'Hter. He does not accept the opinion expressed by General Marcy, 

 in his "Army Life on the Border," that the animal does not require 

 any more water than is contained in the grass roots on which it feeds. 

 The prairie dog towns on the plains are often situated miles away 

 fi-ora any water that can be discovered on the surface, and it is diffi- 

 cult to understand how sufficient moisture could be contained in the 

 food of the prairie dog to replace what must be lost in respiration, 

 &c., and to carry on the process of digestion during the months of 

 September, October and November. At this season of the year it is 

 not unusual for from fifty to sixty days to pass without a drop of rain 

 falling. There is no dew, the air is extremely dry, and the short buf- 

 falo grass (often the only thing which grows on the highlands where 

 the prairie dog villages are commonly found) becomes completely 

 dried down to the roots, while the roots, being but two or three 

 inches under ground, become hard and dry. As tame })rairie dogs 

 are frequently seen to drink water, Mr. Sternberg expresses the 

 belief that in every prairie dog town there is a sufficient number of 

 wells to supply the inhabitants with water. From attempts he had 



