OF ARTS AND SCIENCES. 307 



His next care was to ascertain that the collodion film on the glass 

 underwent no change from shrinking or from hygroscopic moisture. 

 This fortunately proving to be the case, he proceeded to devise an 

 elaborate micrometric apparatus, by which the relative distances and 

 angular positions of the stars uj^on a plate could be precisely meas- 

 ured. With this apparatus, a vast number of measurements have been 

 made, for the results of which astronomers will look with impatience. 

 The plates of the Pleiades have been fully discussed by Dr. Gould, 

 and the work is now, I believe, nearly ready for publication. You 

 will thus perceive that Mr. Rutherfurd is the founder of a new 

 astronomical method of measuring and of recording the positions of 

 stars in groups and clusters, by which an enormous amount of labor 

 in observation may be saved. On a single good night for observation 

 — in our climate there are perhaps three in a year — a sufficient 

 number of plates may be taken to occupy the time of a whole corps 

 of assistants for months, in the subsequent work of micrometric 

 measurement and reduction. The German astronomer, Bessel, spent 

 several years on the group of the Pleiades alone. The whole work of 

 mere observation can now be done in a few minutes. It is true that 

 the micrometric measures which follow are tedious ; but they may be 

 executed at any time, are independent of weather, and require no 

 extraordinary skill, only patient labor. The absolute places of the 

 stars in a cluster are not given by this method. The right ascension 

 and declination of at least one star in the group must be determined by 

 the ordinary methods of observation. The old method and the new are 

 thus mutually dependent. 



Such being the nature of the invention which has been brought to 

 the notice of the Academy, it has been the judgment of the Committee 

 that the case was one coming clearly within the provisions of the trust 

 created by Count Rumford, and consequently that the medals pre- 

 scribed by him for such occasions should be awarded to the inventor, 

 Mr. Rutherfurd. 



And now the moment has arrived when it becomes my agreeable 

 duty, on behalf of the Academy, to present to you. Professor Gibbs, as 

 the chosen, representative of the inventor now absent from the country, 

 the great gold medal and its counterpart in silver, specified by the donor 

 as prizes to be awarded in cases of positive advance in this path of 

 science. I pray you to offer to him our fervent congratulations on his 

 success, as well as our hopes that this testimony may serve as well to 

 him as to others engaged in honorable emulation to fructify these good 



