Royal Society. 391 



them in synchronism with the beats. When standing near the 

 vein we notice a rhythmic movement of the spots of light reflected 

 from it, keeping time with the beats. The alternate retreat and 

 advance of the point where the drops are first formed is executed 

 in the same periods, and is very beautiful. The sensitiveness of 

 this vein is astounding; it rivals that of the ear itself. Placing 

 the two tuning-forks on a distant table, and permitting the beats 

 to gradually die out, the vein continues its rhythm almost as 

 long as hearing is possible. A more sensitive vein might actually 

 prove superior to the ear, — a very surprising result, considering 

 the marvellous delicacy of this organ*. 



By introducing a Ley den jar into the circuit of this powerful 

 induction-coil, I obtain, as those acquainted with the coil well 

 know, a series of dense and dazzling flashes of light, each of 

 inomeDtary duration. Illuminated by these flashes, the drops 

 are rendered distinct, every one of them being transformed into a 

 little star of intense bi'illiancy. They are scattered widely apart. 

 I now call to the jet in the proper tone of voice. It instantly 

 gathers its drops together into a necklace of inimitable beauty. 



In these experiments the whole vein gathers itself into a single 

 arched band when the proper note is sounded ; but by varying 

 the experiment, it may be caused to divide into two or more such 

 bands, as shown in fig. 22. Drawings, however, are ineffectual 

 here; for the wonder of these experiments depends mainly on 

 the sudden transition of the vein from one state to the other. In 

 the motion dwells the surprise ; and this no drawing can render. 



LI. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 314.] 



Feb. 14, 1867. — Lieut. -General Sabine, President, in the Chair. 



THE following communication was read : — 

 " On the Relation of Insolation to Atmospheric Humidity." 

 By J. Park Harrison, M.A. 



t The occurrence of the maxima of insolation on days of great rela- 

 tive humidity which was noticed by Herr v. Schlagintweit in Indiaf, 

 receives confirmation from the fact that the post-solstitial periods 

 of maximum solar radiation in autumn, and also the diurnal maxima, 

 coincide with monthly and daily periods of maximum humidity. 



The following Table of the mean monthly values of solar radiation 

 and vapour-tension for the five months from May to September, at 

 Greenwich, in 1860-64, shows the extent to which this is the case in 

 England %. 



* When these two tuning-forks were placed in contact with a vessel 

 from which a liquid vein issued, the action on the vein continued long after 

 the forks had ceased to be heard. 



t Proceedings of the Koyal Society, 1865, vol. xiv. p. 111. 



\ The vacuum-thermometer was used at Greenwich first in 1860. 



