Natural History. 235 



plants under the microscope, he observed distinct motion in the 

 grains when immersed in water, consisting not only of a change in 

 place, but of form also. Having observed this in the pollen of all 

 the living plants he examined, he next tried to ascertain how long 

 this property continued after the death of a plant, and found that 

 plants dried, or immersed in spirit for a few days, and some even 

 which had been dried for twenty years, and others not less than a 

 century, still exhibited these active particles. Whilst making the 

 observation with the ovula or seeds of the EquisetuTJiy they were 

 accidentally bruised, which very much increased the number of 

 moving particles ; and on bruising the floral leaves and other parts 

 of mosses, they were also obtained. 



With a view of ascertaining whether these active particles, ob- 

 tained from such different parts of plants, were the supposed con- 

 stituents or elementary molecules of organic bodies, different animal 

 and vegetable tissues were examined ; whether living or dead, if 

 bruised in water, they gave moving particles, identical with those 

 of pollen. They were also found in products of organization, as 

 gum resins, vegetable substances, and even pit-coal. The dust or 

 soot deposited on bodies, especially in London, is entirely composed 

 of them. 



As the particles were found in fossil and silicified wood, they 

 were next sought for in inorganic substances, and were at once 

 obtained merely by bruising a small splinter of window-glass upon 

 the stage of the microscope. They were obtained in succession 

 from rocks of all ages, each of the constituents of granite, travertine, 

 stalactites, lava, obsidian, pumice, volcanic-ashes, meteorites, man- 

 ganese, nickel, plumbago, bismuth, antimony, arsenic, and in every 

 mineral that could be reduced to powder sufficiently fine to be tem- 

 porarily suspended in water. In many cases the particles seemed 

 to aggregate into linear arrangements or fibrils, consisting of three 

 or four, and these also had motion. 



Wood, linen, paper, cotton, wool, silk, hair, and muscular fibre, 

 being burnt, gave the molecules as evidently in motion as before 

 combustion. 



The form of these molecules appears to be spherical, but modifi- 

 cations of it occur in certain circumstances ; the diameter of the 

 particles are firom Ysiun^^ ^^ -^siij-s^^^ of ^^ ^'^^^^ 



The principal substances from which these molecules have not 

 been obtained, are oil, resin, wax and sulphur ; such of the metals 

 as could not be reduced to the state of division necessary for their 

 separation ; and finally bodies soluble in water. 



All these observations were made under a simple microscope, 

 and, indeed, with one and the same lens, the focal length of which 

 is about 3^d of an inch. — Phil, Mag. N. S., iv., 161. 



