WITHDSAWN FROM THE ACTION OF GRAVITY. 



235 



genCed to it; but, what is remarkable, although the precaution has been taken 

 of rubbing the whole of the system, (§ 9,) that is, the two faces of the plate as 

 well as its rim, with oil, the oil terminates abruptly at this rim without passing 

 to the other side of the plate, and thus presents a sudden interruption in the 

 curvature of its surface. In the case in question, the new figure acquired by 

 the mass is a portion of a sphere. This portion will be as much larger in pro- 

 portion to the complete sphere as the volume of oil is greater ; but the curvature 

 will always terminate abruptly at the margin of the plate. (See Fig. 2, which 

 represents a section of the solid system and the adherent mass in the case of 

 three different volumes of the latter.) 



The cause of this singular interruption of continuity is readily understood. 

 The rim of the plate reaching to the superficial layer, it is natural that some- 

 thing peculiar should occur along this margin, and that the continuity of form 

 should cease at that point where a foreign attractive action is exerted without 

 transition on the superficial layer. 



14. Let us again make use of the above plate ; but instead of presenting one 

 of its faces to the exterior of the sphere of oil, let us insert the plate edgewise 

 into the interior of this sphere.* The liquid will necessarily extend over both 

 faces of the solid ; and if the diameter of the primitive sphere were less than 

 thxit of the plate, the oil will be seen to form two spherical segments upon the 

 two laces in question, the curvatures of which will still terminate abruptly at 

 the margin of the plate. These two segments may be either equal or unequal, 

 according as the edge of the plate has been introduced into the liquid sphere in 

 such a manner that the plane of the plate passes through the centre of the 

 sphere or not. The upper segment will be slightly deformed by the action of 

 the suspending wire ; but this eftect will be less sensible in proportion to the 

 thinness of the Avire in question. Fig. 3 represents the result of the experiment 

 with two unequal segments. The discontinuity of the curvatures is a very 

 general fact, which Ave shall frequently find to recur in the course of our 

 experiments ; it Avill hereafter lead us to very important consequences. 



/-/^J. 



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7i'ff.5, 



J'icf.G, 



15. I have repeated the same experiment, substituting a plate of an elliptic 

 form for the circular plate. In this, as in the preceding case, the oil extends 

 OA-er both laces of the solid, so as entirely to cover them ; and, if the volume of 



"^ Tliis openition is peifoiuied as follows: The stopper to wliieh the system of the ])lal6 is 

 attached is kept at some distance above the neck of the central aperture, in such a manner, 

 however, that the latter is immersed to a sufficient depth in the alcoholic mixture. The 

 plate can then be moA'cd with tolerable freedom, and it is conducted towards the liquid 

 mass For this purpose the latter ought previously to occupy a suitable position. Imme- 

 diatelj- the l.quid mass is cut, the piate is kept still until the action is terminated, after 

 which the stopper is carefully placed in the neck. A process the reverse to the preceding 

 may also be made use of. The liquid mass is first made to occupy a position near the second 

 aperture, and a sufficient distance from the axis which passes through the centre of the cen- 

 tral aperture; then, having fixed the solid system timdy in the position which it is to occupy, 

 move the liquid mass towards it, and when this has been cut, allow the action to continue 

 uninterruptedly. These processes are also emploj'ed in other experiments, and it is enough 

 to have pointed them out once. In some cases the second is the only practicable one. This 

 may be easily decided upon in making the experiments. 



