philosophical society of washington. 31 



82d Meeting. February 13, 1815. 



The President in the Chair. 

 Forty-three members and visitors present. 

 Mr. F. M. Endlich read a paper 



ON THE coloring AGENT OP GEMS : 



giving analyses of the coloring matter of a great variety of gems 

 and sub-gems, describing in several cases the different changes 

 produced by heating in tl>e open air and when air is excluded, 

 and concluding that iron, chrome, and manganese are the prin- 

 cipal agents in giving color to these minerals. 



Mr. Asaph Hall, on behalf of Rear-Adrairal Davis, Presi- 

 dent of the Commission on the transit of Venus, communicated 



letters 



ON THE OPERATIONS OP THE SEVERAL PARTIES SENT FROM THE 

 UNITED STATES TO OBSERVE THE TRANSIT OF VENUS ON THE 

 8tH of DECEMBER, 1874. 



(abstract.) 



Dr. C. H. F. Peters writes from Queenstown, Otago in New 

 Zealand, that he observed with tlie equatorial the first and second 

 contacts : the former uncertain, the latter with great jjrecision ; 

 none of the much talked of phenomena presenting themselves to 

 his eye. 178 photographs were taken in the interval of these 

 contacts, and 59 while the pLnet was in the disk. The sun was 

 out almost uninterruptedly during the first 1| hours. Then 

 came clouds, with small intervals of sunshine. The last photo- 

 graph was taken 10 minutes before the beginning of egress, and 

 from that time the sun was under a dense cloud, so that the 

 egress was lost. With this exception, the observation of the 

 transit has been successfully accomplished. At all other stations 

 in New Zealand observations were prevented by clouds and rain. 

 The American party escaped disappointment by being at a 

 greater elevation above the sea. 



Capt. Charles W. Raymond, U. S Engineer, gives a full 

 account of his arrangements for observing the transit at Camp- 

 bell Town, Tasmania. Heavy clouds and rain prevented observa- 

 tions of the 1st, 2d, and 4th contacts. The 3d was observed 

 with the equatorial, light clouds drifting over the sun and 

 planet. The planet seemed to gradually assume the pear-shape. 

 Ko shooting out of the planet towards the sun's limb at or near 

 13 



