28 BULLETIN OP THE 



than their perpetual conservation) lies in the static affections 

 either inherent in, or indelibly stamped upon all material elements. 

 The derivative and convertible forms of energy should not, there- 

 fore, be confounded with the primordial and immutable forces 

 resident in the molecule and its atoms — such as cohesive, affini- 

 tive, and gravitative tendencies or affections. 



If molecular attractions and repulsions are really the parents 

 of all dynamic energy, it seems wholly improbable that any form 

 of such attraction or repulsion can ever be the offspring of dyna- 

 mic energy. In other words, we must infer that such exhibitions 

 of molecular attraction and repulsion as those of electricity and 

 magnetism, however seemingly the product and correlatives of 

 motion — as of friction or percussion, of light or heat, of chemical 

 activity or gravitative fall, etc. — are really not so derived, but are 

 to be regarded as being only unveiled or made manifest, from a 

 previous condition of neutralization by a static equilibrium. 



9th Meeting. June 24, 1811. 



The President in the Chair. 

 Prof. A. Hall read a paper 



ON ASTRONOMICAL PHOTOGRAPHY. 



{This paper is published under the title, "On the Application of Photography 



to the Determination of Astronomical Data,'^ in the American Journal 



of Science and Arts (3), vol. ii., pp. 25-30, July, 1871.) 



(ABSTRACT.) 



An account was given in this paper of what had been accom- 

 plished in applying photography to the determination of exact 

 astronomical data. Reference was made to the labors of Messrs. 

 Bond and De la Rue, and it was inferred: (1) that in the case 

 of ordinary observations of double stars the photographic method 

 presents no advantages over the direct method with a filar 

 micrometer or heliometer ; (2) that in the case of an eclipse of 

 the sun, or of the transit of a planet, the results hitherto obtained 

 are such as to give but little confidence in the accuracy of the 

 photographic method. On account of the obvious advantages 

 which the photographic method possesses over the observations 

 of contact in the case of a transit of Venus, provided that the 

 photographic observations can be rigorously and accurately re- 



