83 



new and gradual growth of various parts, to reproduce organs that 

 may have been amputated or injured. He then called on Mr. Morse 

 for information regarding the Mollusks, in answer to the inquiries and 

 suggestions of Mr. Cox. 



Mr. Edward S. Morse stated that many of the fresh-water Snails 

 had the power of rising and falling in the water, by increasing or di- 

 minishing their specific gravity, and that this was done by allowing a 

 portion of air enclosed in the animal to expand or contract, and that 

 the Pearly Nautilus was supposed to make use of the closed chambers 

 of the shell for similar purposes ; but later investigations had shown 

 that this function was not enjoyed by the Nautilus. Mr. Morse then 

 illustrated on the black-board the structure of the fresh-water Snails, 

 and their development from the egg. He also mentioned their pecu- 

 liar habit of crawling on the under surface of the water, and the op- 

 portunity offered to any one of examining their habits, since our 

 brooks and ditches abound with them, and they can be easily kept in 

 confinement. Mr. Morse also made a few remarks on the Pearly and 

 Paper Nautilus. 



A letter was read from Rev. A. B. Kendig, of Davenport, Iowa, 

 who wished for information regarding the cause of the formation 

 of ice in a cave in Decorah, Iowa. This cave is "a mere fissure 

 in the rock, extending in depth from one hundred and fifty to two 

 hundred feet. In this fissure ice forms in summer and disappears in 

 winter. The ice is first found about thirty feet from the entrance, 

 and increases as you advance. The cave was visited on the 14th of 

 September last, and hundreds of pounds of ice was found." 



Mr. Edwin Bicknell accounted for the occurrence of ice in the 

 cave at that time by the theory of the evaporation of moisture. It is 

 a well-known principle in physical science that the conversion of a 

 fluid to the gaseous form is accomplished at a great expenditure of 

 heat, and this, he thought, taken in connection with the naturally low 

 temperature of the earth at that time, would account for the formation 

 of the ice in summer. 



In regard to the disappearance of the ice in winter, the same theory 

 would hold good ; the absence of evaporation in a great measure in 

 cold weather, and the temperature of the earth being at that depth 

 always above the freezing point. In support of the above theory he 

 cited the well-known fact in geology that the temperature of the earth 

 does not undergo any perceptible change in summer or winter, at a 

 depth of from about twenty to one hundred feet from the surface, 

 depending greatly on the latitude of the place in question. He also 

 cited the known effects of the sudden sensation of cold produced by 

 the evaporation of alcohol, or, still better, sulphuric ether, in contact 



