. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. WITHDRAWN FROM THE ACTION OF GRAVITY. 347 gr^ually abswb tlie excess by means of the small syringe, the operation pro- ceeds without difficulty so long as the elements of the meridian line which ter- minate at the edges of the disks deviate considerably from parallelism with the axis ; but when they approximate to this pai-allelism, or, in other words, when we approach the portion of the unduloid which we wish to obtain, it is necessary to
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. WITHDRAWN FROM THE ACTION OF GRAVITY. 347 gr^ually abswb tlie excess by means of the small syringe, the operation pro- ceeds without difficulty so long as the elements of the meridian line which ter- minate at the edges of the disks deviate considerably from parallelism with the axis ; but when they approximate to this pai-allelism, or, in other words, when we approach the portion of the unduloid which we wish to obtain, it is necessary to operate with greater precaution, as the figure might otherwise ciiange spontaneously and disunite. By conducting the operation with care, and, towards the end, removingthe oil only in very small quantities, we arrive, as far as the eye can judge, at the desired portion of the undulqid, (Fig. 7,) a portion which varies in form by approaching or withdrawing from the cylinder, according as the diameter of the disks is greater or smaller relatively to their distance; but then the slightest cause, such as a minute movement communi- cated to the mass by the point of the syringe, is sufficient to produce the gradual alteration and destruction of the figure, which is seen to grow progres- sively thinner near one of the disks, the oil being transferred in greater quantity to the side of the other disk, and the mass finally separates into two parts. From the fact that, in the figure obtained as above, an alteration, occasioned by tlie most trifling cause, proceeds afterwards spontaneously, it would seem that tlie portion of unduloid comprised between the middle of one constricted por- tion and that of the next is at the limit of stability. We see, from what has just been said, why, in § 4, the adoption of a cylin- dei' as a solid system was recommended. With disks, there is need of the greatest circumspection and care to arrive at the point where the last elements of the meridian line a
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