662 Transactions of the Society. 



the colloid, e. g. decomposition or heat ; or by the existence in one 

 colloid of a higher molecular composition than in another — albumen, 

 for instance, having a greater power, even when coagulated, than 

 gelatin or gum. Conversely, dilution, coagulation, condensation, 

 cold, magnetism, all hinderers of vibration, hinder sphere-formation. 



Quite recently I have been able to illustrate these influences by 

 experiments, which show the movements of molecules translated 

 into large movements visible under the Microscope, and in one case 

 visible to the naked eye. These experiments are before another 

 Society and I am not in a position to quote them at present.* 



To sum up, therefore, while I admit that heat, electricity, 

 capillary attraction, chemical and other forces may each or all 

 play a part in producing Brownian movements ; while I admit 

 the agency of surface-tension; while I do not altogether reject 

 Mr. Eainey's theory of persistent movements in fluids,! I claim the 

 intestine vibration of colloids as in many cases an agent in the pro- 

 cess, and more especially in the fluid and semi-fluid parts of animal 

 and vegetable organisms. 



Indeed I am disposed to go further, and to regard this as in 

 one aspect a manifestation of a tendency, already glanced at, in all 

 molecules to come to rest — to rest of a physical or chemical kind ; 

 and of all molecules of one kind to find rest in association with 

 their kind, as in the crystal. Slow movements of this kind have 

 been at work in the yet piilpy chalk separating the flints from it. 

 Slow movements of the kind are abundantly illustrated in the 

 metamorphoses of minerals. Quicker movements are seen in the 

 mixture of the kaolin and distilled water ; quicker still in kaolin 

 with soap. As I see crystalloids struggling in the grasp of colloids, 

 and gradually extricating themselves from their grasp to revert to 

 the crystalline from the spherical form, with constant accompani- 

 ment of molecular movements, I see the existence of a chain of 

 force leadiug from the activity of movement which builds up the 

 sphere to the rest which is possible only to the inorganic crystal, 

 and compare this chain with the chain seen in the vaporization of 

 water by the sun, the lifting of the vapour to the upper regions 

 of the atmosphere, its condensation to cloud, and its subsequent 

 descent in rain or in rivers to rest in the sea. As the one chain 

 produces a series of actions and expenditure of power in the outer 

 world, so in the economy of living organisms some such chain as 

 I have compared with it may well play its part in development, in 

 organization, in motion. 



* See a paper since read before the Royal Society (June 19th, 1879), entitled 

 " A-ii account of Experiments on the Influence of Colloids upon Crystalline Form, 

 and on INIovemcnts observed in Mixtures of Colloids with Crystalloids." 



t See St. Thomas's Hospital Reports, vol. ii. 1871, " On Continued Move- 

 ments iu Fluids." 



