3 5 o Mr. Henry's Conftderations on different Materials, 



ent circumftances, are requifite for thefe feveral 

 materials. M. du Fay's experiment, which he 

 made before the Royal Academy of Sciences, has 

 been fo often related, that I fhall not quote the 

 particulars. Let us rather refer to the theories 

 which have been advanced to account for thefe 

 phenomena; inquire how far they appear to be 

 founded on truth ; and give the chemical analyfes 

 of the various fubftances, which may perhaps 

 ferve to throw fome new light on the fubjed. 



Thefe phenomena have been varioufly ex- 

 plained. Some have attributed the variety in 

 the power of the feveral fubftances to retain the 

 dying ingredients applied to them, to the differ- 

 ent ftru6ture of their filaments j to the porofity 

 of wool, and to the impenetrability of cotton 

 and linen* ; at leaft, to the latter pofTcfling 

 pores of much inferior dimenfions j filk being 

 fuppofed to hold a middle rank. Wool, fay 

 thefe theorifts, is compofed of numerous fila- 

 ments, fimilar to hairs, and like them confifting 

 of tubes, containing a medullary or oily matter. 

 The fides of thefe tubes are alfo perforated with 

 an infinite number of fmall orifices, communica- 

 ting with the longitudinal canal. From this 

 mechanifm, it is excellently adapted for receiving 

 extraneous bodies, which are not only capable of 



• Le Pileur d'ApHgny Art de la Teinture des fils, & 

 etoiFes de Colon. 



being 



