WITHDRAWN FROM THE ACTION OF GRAVITY. 605 



about I a millimetre. A much finer wire might have been used 

 with the same success ; but the apparatus would then become 

 inconvenient, on account of the facility with which it would be 

 put out of shape. By operating with care, the curvatures of the 

 lens may be diminished so as almost to make them vanish ; thus 

 I have been enabled to reduce the lens which I formed, and the 

 diameter of which, as I have stated, was 7 centimetres, to such an 

 extent that it was only 2 or 3 millimetres in thickness. Hence 

 we might presume that it would be possible to obtain, by a proper 

 mode of proceeding, a layer of oil with plane faces. This is, in 

 fact, confirmed by experience, as we shall see further on. 



19. To render the curvatures of the liquid lens very slight, 

 the point of the syringe must naturally be applied to the middle 

 of the lens, because the maximum of thickness exists there. 

 Now when a certain limit has been attained, the mass suddenly 

 becomes divided at that point, and a curious plijenomenon is 

 produced. The liquid rapidly retires in every dii-ection towards 

 the metallic circumference, and forms a beautiful liquid ring 

 along- the latter ; but this ring does not last for more than one or 

 two seconds, after which it spontaneously resolves itself into 

 several small, almost spherical masses, adhering to various parts 

 of the ring of iron wire, which passes through them like the 

 beads of a necklace. 



20. The reasoning which led us, at the commencement of 

 paragraph 18, to reduce the primitive solid system to a simple 

 metallic wire representing the line in the direction of which this 

 system is met by the superficial layer belonging to the new 

 figure of equilibrium, may be generalized. We may conclude, 

 that whenever a solid system introduced into the mass is not 

 met by the superficial layer of the figure produced, except- 

 ing in the direction of small lines onl3% simple iron wires, repre- 

 senting the lines in question, may be substituted for the solid 

 system employed. But if the volume of the primitive solid sy- 

 stem were considerable, it would evidently be requisite to add to 

 the mass of oil an equivalent volume of this liquid, to occupy the 

 place of the solid parts suppressed. 



There is however an exception to this principle ; it occurs 

 when the solid system separates the entire mass into isolated 

 portions, as in the experiment of paragraph 14 ; for then these 

 portions assume figures independent of each other, and which 

 may correspond to different pressures. In this case the sup- 



