234 TKANSACTIONS OF THE [mAY 17, 



May 17, 1886. 

 Stated Meeting. 

 The President, Dr. J. S, Newberry, in the Chair. 

 One hundred and ten persons present. 

 Prof. C. A. Young read a paper entitled 



TEN years' progress IN ASTRONOMY, 



1876-1886. 



TJie Earth. 



In what may be called the astronomy of the earth, there is no 

 very great discovery, nothing extremely new and brilliant to 

 record during the past decade ; but there has been considerable 

 and steady progress. 



a. As regards the earth's form and dimensions, it has become 

 quite certain thatBessel's ellipticity (3-^0) is too small. Clarke's 

 value of gij is now admitted and employed on the U. S. Coast 

 Survey with a decided improvement of accordance. A slightly 

 larger value even is suggested by the most recent pendulum ob- 

 servations, and ^1^ is now adopted in Europe. 



One of the most important steps in this branch of investigation 

 is the discovery, by Mr. Pierce (of our own Coast Survey), of the 

 large correction required in many former pendulum determina- 

 tions, on account of the yielding of the stand from which the 

 pendulum is suspended. 



During the past ten or fifteen years, a great amount of mate- 

 rial has been collected towards a complete gravitational survey 

 of the earth, by the work of Lieut. -Col. Herschel in India, and 

 of the officers of the Coast Survey in this country and elsewhere, 

 and a very important part of it has consisted in connecting the 

 older work with the new, by Peirce's operations in Europe, and 

 those of Herschel, in this country. 



At the same time it has become increasingly evident that very 

 little is now to be gained by endeavoring to find a spheroid fitting 

 the earth's actual form more closely. It will be best simply to 

 adopt some standard (say that of Clarke, but it makes very little 

 difference what), and to investigate hereafter the local devia- 

 tions from it. These deviations seem to be larger and more ex- 

 tensive than used to be supposed, the station errors in latitude 

 and longitude being at least quantities of the same order as the 

 variations of elevation. 



We mention, in passing, the investigations of Fergola, based 



