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affects sensible masses of fluid, and is the only one of the movements 

 which can be correctly described as a current. It is osmose, and the 

 work of the osmotic force to be discussed. 



As diffusion is always a double movement while salt diffuses 

 out, a certain quantity of water necessarily diffusing in at the same 

 time in exchange diffusibility might be imagined to be the osmotic 

 force. But the water introduced into the osmometer in this way 

 has always a definite relation to the quantity of salt which escapes, 

 and can scarcely rise in any case above four or six times the weight 

 of salt, while the water entering the osmometer often exceeds the 

 salt leaving it, at least one hundred times. Diffusion is therefore 

 quite insufficient to account for the water current. 



The theory which refers osmose to capillarity appears to have no 

 better foundation. The great inequality of ascension assumed among 

 aqueous fluids is found not to exist, when their capillarity is cor- 

 rectly observed : and many of the saline solutions which give rise 

 to the greatest osmose are undistinguishable in ascension from pure 

 water itself. 



Two series of experiments on osmose were described, the first 

 series made with the use of porous mineral septa, and the second 

 series with animal membrane. The earthenware osmometer con- 

 sisted of the porous cylinder employed in voltaic batteries, about 

 5 inches in depth, surmounted by an open glass tube 0'6 inch in dia- 

 meter, attached to the mouth of the cylinder by means of a cap of 

 gutta percha. In conducting an experiment the cylinder was filled 

 with any saline solution to the base of the glass tube, and immediately 

 placed in a large jar of distilled water ; and as the fluid within the 

 instrument rose in the tube, during the experiment, water was added 

 to the jar so as to prevent inequality of hydrostatic pressure. The 

 rise (or fall) of liquid in the tube was highly uniform, as observed 

 from hour to hour, and the experiment was generally terminated in 

 five hours. From experiments made on solutions of every variety of 

 soluble substance, it appeared that the rise or osmose is quite insig- 

 nificant with neutral organic substances in general, such as sugar, 

 alcohol, urea, tannin, &c. ; so also with neutral salts of the earths 

 and ordinary metals, and with chlorides of sodium and potassium, 

 nitrates of potash and soda and chloride of mercury. A more sen- 

 sible but still very moderate osmose is exhibited by hydrochloric, 



