196 Miscellaneous Intelligence. 



bf A, is greater than that of A for itself. As to the action of tlie 

 canal on the portion rt, 6, that will be equal, and exerted in con- 

 trary directions at its two extremities ; it will not, therefore, be 

 either adverse or favourable to the movement of the fluid in the 

 canal : and the same will be the case with respect to the pressures 

 exerted at a and 6, by the external liquids, as long as they are 

 equal : nevertheless, the action of the canal, and the external 

 pressures, will prevent the thread of fluid from being broken, so 

 that it will move without interruption in the direction in which it 

 is drawn by the greatest attraction, or from a to 6. Hence will 

 result an elevation of the level of B, and, consequently, an increase 

 of pressure at the extremity 6, of the passage, and this elevation 

 "will proceed until the difference of pressure in a and b shall be 

 equal to that of the attractions exerted by the two fluids A and B, 

 on the thread a b; this effect will be produced the more rapidly 

 as the division is pierced with a greater number of passages similar 

 to that which has been considered. 



Now let us examine what would occur if the division were formed 

 of two others different in their nature, and exactly superposed ; ex- 

 erting no action on one of the liquids, B for example, and one only 

 acting on the other liquid. The liquid B will then retain its ori- 

 ginal position undisturbed ; in consequence of the action it exerts 

 upon itself it cannot penetrate the canal a 6, just as mercury can- 

 not escape by a capillary aperture made in a barometer-tube. It 

 will be the same with A, when that face of the division which exerts 

 no action upon the liquid is turned towards it ; so that how nu- 

 merous soever the apertures, the two liquids would, under such 

 circumstances, remain separate and preserve their original level. 

 But if the division be turned so that the face which acts upon A 

 shall be in contact with that liquid, it will penetrate the canal a b 

 by means of capillary attraction ; ^and the velocity which the liquid 

 urged by this force may acquire, may make it pass that point in the 

 canal where the division changes its nature, and even make it reach 

 the extremity in the liquid B, so that it is possible that the liquid A 

 should entirely fill the canal a b, as in the case which has already 

 been examined. Then if we always suppose the attraction of B for 

 A to be superior to that which A has for itself, the thread a b will 

 flow into B until the level of the latter is so far altered that the 

 excess of pressure at b can balance the difference of attractions ex- 

 erted by the two liquids at a and b. 



M. Poisson then observes that, without pretending to assign a 

 cause, exclusive of all others, for the phenomena of absorption by 

 vegetable and animal membranes observed by M. Dutrochet, his 

 object is to show that effects which have at least a great resem- 

 blance to these important phenomena, may be produced by capil- 

 lary action conjoined with the difference of affinity existing between 

 heterogeneous substances without the assistance of electricity, either 

 moving or quiescent. It appears that M. Dutrochet afterwards 



