ACADEMY OF SCIENCES. 143 



end of summer, by assuming that rains had swollen their sources, 

 and these, by hydrostatic pressure through underground conduits, 

 had raised their distant outlets. 



Prof. Davidson said the theory of Judge Hastings was unsup- 

 ported by facts. Earthquakes are not confined to di-y, warm 

 countries. They are common in Alaska, in a climate of perpetual 

 moisture. 



Dr. H. Gibbons pronounced the explanation of the rise of springs 

 and streams as equally untenable, and ascribed it to the diminution 

 of evaporation with the shortening of the days and the lengthening 

 of the nights ; a view in which he was supported by Dr. Cooper and 

 Dr. Kellogg. He had treated that subject in an elaborate paper, 

 Avhich was published in Silliman's Journal some twelve years ago, 

 and his explanation had been accepted by scientific men as correct. 



Dr. Kellogg related the results of experiments to test the amount 

 of evaporation from the earth, which was ascertained to be very 

 great in the dry est season. Of course, when this evaporation was 

 lessened by shorter days, there would be a gradual increase in 

 springs and streams. 



Dr. Blake thought that the contraction of rocks, with lessened 

 heat, might, by reopening fissures, permit a greater flow of water ; 

 and commented upon the increase of streams after an earthquake 

 shock as the result of the opening of cracks. 



Dr. Gibbons said that the increase of water occurred with the 

 shortening days when there was no abatement of heat, and he 

 rather referred the flow coincident with earthquakes to the settling of 

 the soil and rocks, which would squeeze out the moisture or close its 

 ordinary channels of escape under the surface. 



Judge Hastings observed that he advanced his theory only to 

 elicit discussion, but he thought he could vindicate it. In reply to 

 a question from Dr. Gibbons, he said that he was first led to attribute 

 earthquakes to the falling in of cavern walls by a fact told him six 

 months ago by one of the Sisters at San Juan Capistrano, who 

 showed him Avhere the hill had sunk in at the time of the earthquake 

 which destroyed the Mission Church in 1813. 



Dr. Le Plongeon made some remarks on earthquakes in Peru, 

 and endorsed an opinion advanced by Dr. Gibbons, that such 

 phenomena were caused by the explosion of gases along spaces 

 between the molten core of the earth and its crust. 



