OF ARTS AND SCIENCES : NOVEMBER 8, 1871. 333 



John Trowbridge, of Cambridge, to be a Resident Fellow in 

 Class I., Section 3. 



J. A. Allen, of Cambridge, to be a Resident Fellow in Class 

 II. , Section 3. 



William H. Pettee, of Cambridge, to be a Resident Fellow 

 in Class II., Section I. 



John K. Paine, of Cambridge, to be a Resident Fellow in 

 Class III., Section 4. 



Edwin P. Seaver, of Cambridge, to be a Resident Fellow in 

 Class I., Section I. 



Professor Benjamin Peirce made a communication on the 

 effect of the consistency of the interior of the earth on the 

 Precession of the Equinoxes. Mr. Hopkins claimed that the 

 effect of the fluidity of the interior would be to render the pre- 

 cession much greater. This view was controverted by Mon- 

 sieur Delaunay, but sustained by Mr. Pratt. Professor Peirce 

 maintained that, owing to friction, a certain velocity would be 

 imparted to the interior, even if liquid, so that it would pro- 

 duce the same effect as if solid. 



Dr. Charles Pickering stated that, having seen the earth's 

 crust forming, he would make a few remarks on the subject : 



At the time of his visit to Hawaii there were two lakes of liquid 

 lava at the bottom of the Great Crater ; the larger lake remained 

 always liquid, but the smaller one, " two hundred feet " in diameter, 

 occasionally congealed over. Here is one point gained : for it has been 

 argued, that the material of the Earth, if once entirely fluid, in cooling 

 would contract, become heavier, and sink ; therefore forming a crust is 

 impossible. It is forgotten that a perfectly dry cambric needle can be 

 placed on water so as to float, and for the reason, that it displaces more 

 of the water than its own bulk. So in the irregularities of the earth's 

 surface commonly attributed to the cooling material contracting, we can 

 distinguish a general tendency to concavity, proportionably diminishing 

 and counterbalancing increase in weight. 



To return to the smaller lava-lake, when the congealed crust broke 

 up, there was a different state of things. In thickness, this crust seemed 

 six or eight inches ; and back from its edge, usually several feet, a 

 crack would make its appearance, showing a red glow from beneath ; 



