4 Mr. J. J. Waterston on Capillarity 



wciglit descending througli one inch, is the work that denudes 

 two square inches of aqueous surface. The vohime of water 

 equivalent to this weight divided by 2, ought to be about ^i^- 

 of a cubic inch, if the quotient (Q) of surface developed by the 

 work performed is the same as in the first series of observations. 

 To try this, a slip of paper 10 inches long and half an inch 

 broad, with clean cut edges, was formed into a spiral having about 

 a quarter of an inch between each convolution. It was then fixed 

 ^vith lac upon a thin piece of plate glass while heated. The 

 lower edge of the paper was thus firmly established in a plane 

 parallel to the plate, and the whole suspended from the pan of a 

 delicate balance, and adjusted by means of a plate and spirit- 

 levels, so as to hang with the lower edge of the paper perfectly 

 level. The paper spiral was now immersed a quarter of an inch 

 in a shallow vessel of distilled water and allowed to soak ; the 

 level of the surface of the water being adjusted so that the spiral 

 edge of the paper should separate from it at the tu.rn of the beam. 

 Thus arranged, the difference of weight just at the separation 

 and immediately after, was found by repeated careful observa- 

 tions to be exactly 38 grains. This being the weight of 0-1505 

 cubic inch of water (at the temperature 86°), shows the volume 

 raised by a water-line 20 inches long. For one inch the volume 



is — i^ — = 0'00752, or of a cubic inch. The value of Q 



thus determined is 132"9. 



§ 5. The generally recognized fact, that the power of capillary 

 suspension resides at the water-line — that the weight of the whole 

 coliunn hangs, as it were, upon the water-line, and is equili- 

 briated by the cohering energies of one ring-line of molecules, — 

 is clearly brought out by the following experiment. 



A column of water in a capillary tube was drawn out of it by 

 pressing the lower end on an absorbing surface until only a small 

 portion was left. It was then brought down to touch a surface 

 of alcohol. The column rose in the tube, having a small portion 

 of air separating the water from the spirit ; and the height 

 attained by the capillary column exceeded that of the water alone 

 exactly in the inverse ratio of the specific gravities of the two 

 liquids. The spirit soon drew down the small heading of water 

 over the wet surface of the tube ; and it was interesting to ob- 

 serve, tliat, at the instant when it all disappeared, the column 

 tumbled down to the level proper to spirit, which in fine tubes 

 is only about four-tenths that of water. In the same way, when 

 s])irit forms the heading, the column sprung up at the instant 

 that the upper line of spirit had disappeared. This experiment 

 was repeated with other liquids, and the result could always be 

 anticipated from the specific gravity and specific capillarity. 



