ON ACTIVE MOLECULES. 471 



the various animal and vegetable tissues, whether living or 

 (lead, they were always found to exist P and merely by 

 bruising these substances in water, I never failed to disen- 

 gage the molecules in sufficient numbers to ascertain their 

 apparent identity in size, form, and motion, with the smaller 

 particles of the grains of pollen. 



I examined also various products of organic bodies, par- • 

 ticularly the gum resins, and substances of vegetable origin, 

 extending my inquiry even to pit-coal ; and in all these [9 ^ 

 bodies Molecules were found in abundance. I remark here 

 also, partly as a caution to those who may hereafter engage 

 in the same inquiry, that the dust or soot deposited on all / 

 bodies in such quantity, especially in London, is entirely 

 composed of these molecules. 



One of the substances examined, was a specimen of fossil 

 wood, found in Wiltshire oolite, in a state to burn with 

 flame J and as I found these molecules abundantly, and in 

 motion in this specimen, I supposed that their existence, 

 though in smaller quantity, might be ascertained in mine- 

 ralized vegetable remains. With this view a minute portion 

 of silicified wood, which exhibited the structure of Coniferae, 

 was bruised, and spherical particles, or molecules in all 

 respects like those so frequently mentioned, were readily 

 obtained from it ; in such quantity, however, that the 

 whole substance of the petrifaction seemed to be formed of 

 them. But hence I inferred that these molecules were not , 

 limited to organic bodies, nor even to their products. 



To establish the correctness of the inference, and to 

 ascertain to what extent the molecules existed in mineral 

 bodies, became the next object of inquiry. The first sub- " 

 stance examined was a minute fragment of window-glass, 

 from which, when merely bruised on the stage of the mi- , 

 croscope, I readily and copiously obtained molecules agree- 

 ing in size, form, and motion with those which I had already 

 seen. 



I then proceeded to examine, and with similar results, 

 such minerals as I either had at hand or could readily ob- - 

 tain, including several of the simple earths and metals, with 

 many of their combinations. 



