originality of his deceased friend. "Many 

 years ago," so he wrote, " the Rev. John 

 M ichell of this Society contrived a method 

 of determining the density of the earth, 

 by rendering sensible the attraction of 

 small quantities of matter ; but as he was 

 engaged in other pursuits, he did not 

 complete the apparatus till a short time 

 before his death, and did not live to make 

 any experiments with it. After his death 

 the apparatus came to the Rev. Francis 

 John Hyde Wollaston, Jacksonian Pro- 

 fessor at Cambridge, who not having 

 conveniences for making experiments 

 with it, in the manner he could wish, 

 was so good as to give it to me." 



" The apparatus is very simple : it 

 consists of a wooden arm, 6 feet long, so 

 as to unite great strength with little 

 weight. This arm is suspended in an 

 horizontal position, by a slender wire, 

 40 inches long, and to each extremity is 

 hung a leaden ball, about 2 inches in 

 diameter, and the whole is enclosed in 



