[ 16S ] 



XXIX. Experiments on the Adhesion of Nails. By 



B. Bevan, Esq. 



To the Editors of the Philosophical Magazi?ie and Journal. 



Leighton Bussard. 



NAILS of various kinds have been used for many cen- 

 turies, in almost every part of the world, and constitute 

 one of the most general modes of fastening substances together. 

 Every carpenter is familiar with the use of the nail, and pos- 

 sesses a practical knowledge, more or le'ss accurate, of the 

 force of adhesion of different nails and in different substances, 

 so as to decide without difficulty, what number, and of what 

 length, may be sufficient to fasten together substances of va- 

 rious shapes, and subject to various strains. But so far as 

 my inquiries have been made, I have not been able to find 

 any authentic experiments, of the real force of adhesion of 

 different nails, when driven into wood of different species; or 

 to learn the actual weight, without impulse, necessary to force 

 a nail a given depth into wood, and also the proper force re- 

 quired to extract the same when so driven. With a view to 

 obtain some useful knowledge upon this elementary mechani- 

 cal question, I had a machine constructed to meas.ure the 

 force of pressure and tension with extensive power, and ap- 

 plied it to the extraction of nails of different lengths* from a 

 quarter of an inch to two and half inches. 



Theoretical investigation points out an equality of resist- 

 ance to the entrance and extraction of a nail, supposing the 

 thickness to be invariable ; but as the general shape of nails 

 is tapering towards the points, the resistance to entrance 

 becomes of necessity greater than that of extraction : — in some 

 of my experiments I have found the ratio to be about 6 to 5. 



The following abstract will exhibit the relative adhesion of 

 nails of various kinds, when forced into dry Christiana deal, 

 at rio-ht angles to the erain of the wood. 



The 



