RESIDUO-CAPILLARY ATTRACTION. 225 



carried up by its specific levity, but rather adhere to the membrane 

 in the way that bubbles of air adhere to the sides of vessels containing 

 water or mercury. But, be this as it may, the end of the tube which 

 communicates with the endosmometer, will soon be surrounded by a 

 stronger infusion of the treacle, which will again bring the residual 

 force into action ; thus a fresh portion of the fluid will be introduced 

 into the endosmometer, and the same process will be repeated as before. 

 For the sake of explanation, I have supposed the residual force to 

 produce its eflPect discontinuously, but it is easy to see that the process will 

 really be continuous, the united actions of the endosmose and exosmose 

 always keeping the orifices of the tube surrounded by fluid in such a 

 state of dilution that the magnitude of the residual force will be exactly 

 sufficient to create a supply proportioned to the demand arising from 

 the mixing process which is continually proceeding within the endosmo- 

 meter. The residual force cannot be less than this, for if it were, the 

 encroachment of the treacle upon the issuing orifice would immediately 

 increase it ; nor can it be greater, for then the accumulation of the more 

 diluted fluid at that same orifice would immediately diminish it, 



23. The quantity transmitted in a given time must depend more 

 upon the rapidity with which the mixing process is carried on within 

 the endosmometer than on the magnitude of the residual force. This 

 force is certainly essential to the transmission, but its effect is no other 

 than that of a pump which supplies the fluid from below as fast as it is 

 wanted, and no faster, and that of a catch or valve to sustain it when it 

 is once elevated. The moving force at the summit of any protruding 



spicula is by No. (14) represented by [^ + ~p) ^(p — ^)^ and is, 



therefore, for spicule of given shape, as the square of the difference 

 of densities. It might appear then, at first sight, more probable that 

 the quantity of the lower fluid absorbed by the fluid in the endosmo- 

 meter in a given time, would be more nearly as the square of the 

 difference of densities, than as the simple power of this difference, which 

 is the law the experiments of Dutrochet tend to establish. But such 

 a conclusion would be very precarious, as will appear by the following 

 considerations. 



