250 PROCEEDINGS OF THE AMERICAN ACADEMY 



from those edges towards the centre of the planes, such as is 

 exhibited in crystals of alum partially dissolved by elevation 

 of the temperature of the mother solution in which the crys- 

 tals were originally formed. 



He stated that he had examined and assayed some remarka- 

 ble specimens of native gold from California, one single mass 

 examined by him weighing 265 ounces, and containing 235 

 ounces of California gold, or 200 ounces of fine gold, and 35 

 ounces of silver. This single specimen is worth ,^3,885, and 

 is the largest that has been brought from California to this 

 city. 



Dr. J. C. Warren exhibited to the Academy some large and 

 valuable casts of fossils from the Sivalik Hills, situated in the 

 northern part of Hindostan, which he described and remarked 

 upon at considerable length. 



Mr. J. D. Whitney gave an account of the progress of the 

 geological survey of the United States mineral lands in Michi- 

 gan, and of its results ; and exhibited several geological maps 

 of that region executed for the United States. 



Three hundred and forty-first meeting. 



January 7, 1851. — Monthly Meeting, 



The President in the chair. 



Professor Peirce made some remarks respecting the uncer- 

 tainty existing in regard to the masses of the planets. They 

 vary when determined by different satellites, and should be 

 taken as determined by actions upon planets, rather than upon 

 satellites. The observations of Mr. Bond upon the satellite 

 of Neptune give a less mass to that planet than those of the 

 Pulkova Observatory, or those of Mr. Lassell ; but the accuracy 

 of Mr. Bond's observations is confirmed by the perturbations 

 of Uranus. Professor Peirce stated the amount of discrepancy, 

 as to the masses of several of the planets, between observation 

 and theory. He said that theoretical errors could sometimes 



