ADDITION, BY THE TRANSLATOR. 



WHOEVER pciuCcs Mr. Leeuwcnhock's Works, will find difplayed in 

 them niucii found philofophical knowledge, of which funic inftanccs appear 

 in the preceding JLffay. Thel'e I fhall quote, in order to explain tholcparts 

 in them, which may appear difficult to fome of my readers. In page 171, the 

 author tells us, that the fubflancc inclofing the young plants of Wheat, ap- 

 pears of a different colour from the meal)' part of the grain, by rcafon that 

 the globules which compofe it are not, fingly, fo pellucid, and therefore do not, 

 altogether, appear fo white, as the meal ; and in p. 179 he reflefis, with admi- 

 ration, how clofely compared mult be ilie fniallell component particles of 

 the globules of meal, to give them that tranfparency. To thofe, who are not 

 conyerfant in optics, it may appear ftrange, that the moft tranfparent bodies 

 have the fmalleft pores, and, that a collc6tion of fmall tranfparent globules 

 fliould altogether exhibit a white colour, but this is according to the cfla- 

 bliflieddo8rine of light and colours, of which Mr. Leeuwcnhoek appears to 

 have been fully informed. 



As to the firft, Sir Ifaac Newton has flicwn, that it is not the largenefs of 

 the pores of bodies which makes them tranfparent, but the equal dcnfity or 

 continuity of their parts; which, he fays, appears from hence, that all opake 

 bodies immediately begin to be tranfparent, when their pores become filled 

 with a fubftance of equal or almolt equal denfity, with their parts : thus pa- 

 per, dipped in water or oil, linen cloth deeped in oil or vinegar; and other 

 fubftances, foaked in fuch fluids as will intimately pervade their little pores, 

 become more tranfparent than before. 



As to the fecond, white being a compofition of all colours, a colleBion of 

 tranfparent globules, which, from their furfaces reflcft the light in all direfti- 

 ons, will produce whitcnefs by that refleBion. This is feen in the froth on 

 liquids, and particularly foap-fuds, which is nothing but a compofition of 

 jninute globules of water, made tenacious by the foap. 



