J 88 Prof. Draper 07i Capillari/ Attraction. 



B, not more than the tenth of an inch. Tubes of this kind 

 are used to exhibit the ordinary phaenomena 

 of capillary attraction. 



Fill the siphon to a given altitude, A B, 

 with quicksilver; the metal of course does 

 not rise in the narrow branch, B, to its hy- 

 drostatic level, for mercury is depressed in a 

 capillary tube, inasmuch as it cannot wet 

 glass. Introduce a small column of water, 

 B c. The mercury may now be regarded as 

 being in contact with a tube of water, because that liquid wets 

 the sides of the glass, intervening between it and the mercury. 



Pass a slender platina wire, x, down the tube so as to touch 

 the water; let it be in communication with the positive elec- 

 trode of the voltaic battery : with the negative electrode touch 

 the mercury in the wide branch of the siphon A, and in an 

 instant the metal will rise in the narrow tube, and fall again 

 to its former position as soon as the current is stopped. 



U 



III. Admitting the correctness of this theory, we can give a 

 very clear explanation of several curious facts. 



1st. Huygensobserved, that mercury might be made to stand 

 in a narrow barometer tube at an altitude of seventy inches. 



This deviation from the true level appears to depend on the 

 cleanliness of the interior of the tube, and most barometers are 

 liable to it to a small extent. By tapping upon the case the 

 adhesion is overcome, and the mercury falls to its proper level. 



If this movement is accomplished in the dark, a pale flash of 

 electric light attends it. I infer, therefore, that the mercury 

 adheres to the tube, simply because the one is positive and the 

 other negative; a disturbance which took place upon contact. 



2nd. P. Abat noticed, that if in an inverted siphon of uni- 

 form diameter some mercury is poured, and the siphon in- 

 clined so as to make the mercury flow up one of the branches, 

 on restoring it to the vertical the metal does not return to its 

 hydrostatic level, but remains elevated to a certain extent. 

 The reason is probably the same as in the foregoing case. 



3rd. When a large globule of quicksilver is placed in a 

 watch-glass beneath some water containing a little ammonia, 

 the metal being placed in relation with the negative, and the 

 water with the positive electrode, the figure of the mercurial 

 globule changes, and it becomes ellipsoidal. This is due to an 

 increased pressure between the metal and the water, a pressure 

 which is unequal at the different points of contact, being at a 

 maximum in those regions nearest the positive electrode. 



At the same time currents are seen traversing the water in 



