Briggs.] 278 [December. 



Stated Meeting, December 4:th, 1863. 



Present, eighteen members. 

 President, Dr. Wood, in the Chair. 



Professor McClune, recently elected a member, was intro- 

 duced to the President, and took his seat. 



Letters were received from the Massachusetts Historical 

 Society, acknowledging publications, and from M. Boucher 

 de Perthes, of Abbeville, in France, announcing a donation 

 to the Society. 



Donations for the Library were received from Profs. Silli- 

 man and Dana, the Essex Institute, Prof. Geo. Ticknor, and 

 the London Reader. 



Mr. Briggs made a communication on the application of 

 mathematics to the screw, pointing out certain striking coin- 

 cidences between the results as computed and as obtained by 

 experiment. 



Mr. Briggs wished to communicate to the Society some curious 

 results which had been obtained in an investigation he had made of 

 the strength and the application of forces to the screw-bolt as ordi- 

 narily in use by mechanics. He had found first, that the propor- 

 tions established h^ practice as to the number of threads upon any 

 given diameter of bolt, were those which could be derived from a 

 straight line formula. Thus, Mr. Whitworth's result in collating 

 the practice of English engineers in this respect, could be (with the 

 exception of the half inch bolt, which was too coarse), expressed 



1 



by the formula — j-r — , where, 



d = diameter of belt, 

 a = a coefficient, 

 c :=: a constant. 



On proceeding further in the investigation of the subject, he found 

 that every part of the bolt, the diameter of the root of the threads, 

 the heads, the proportions of the nut, &c., was capable of being 

 expressed in a general formula, instead of taking each particular size 

 in the calculations he was desirous of instituting. The general 

 formula of the screw is laid down in most works on applied mechan- 

 ics, and has the following cumbrous shape. 



