Surron—Study of Evaporation from Water-Surfaces. 178 
This particular experiment was made in April—one of our 
most humid months. It appears that the sand evaporated much 
more rapidly than the clay for the first week, but afterwards, 
when of course it had less to lose, it lost less. By the twenty- 
eighth day both earths were gaining or losing according to the 
humid state of the air. The minus signs on the last line stand 
for gains. 
Before closing this already lengthy paper there is one point 
which, although somewhat foreign to its main purpose, may not 
be without interest: will an electrified water-surface evaporate 
more or less than an unelectrified one? About the middle of the 
eighteenth century the Abbé Nollet, experimenting with capillary 
tubes, came to the conclusion that all organized bodies (which 
according to his view were to be considered as assemblages of 
capillary tubes) evaporated or perspired more when electrified 
than usually. He also “ electrified liquors of all sorts in open 
vessels, and remarked that the electrification augmented their 
evaporation, in some more, in others less, according to their 
different natures.” He justly observed, however, that it is not so 
easy a task to draw a safe conclusion from the experiments as 
might at first be imagined.’ In commenting upon and criticising 
Nollet’s results, Ellicot quoted some experimental work of his own 
from which he concluded that an increased flow through capillary 
tubes did not depend upon a mere electrification of the water, 
but upon the passage of an electric current.” A few years later 
Bohadsch repeated and confirmed Nollet’s results. He found 
that 4 oz. of river-water exposed in a glass vessel of 4 inches 
diameter and electrized five hours lost in their weight 8 grains. 
But 4 oz. of river-water in the same kind of glass, but not 
electrized, lost in the same time only 3 grains. Hence he con- 
cluded that electricity augments the natural evaporation of liquids, 
and operates in vessels of metal more strongly than in those of 
glass.° 
J.J. Thomson remarks that “few direct experiments on the 
evaporation of electrified water-surfaces seem to have been made. 
Mr. Crookes, from some experiments he made on this point, came 
to the conclusion that a negatively electrified surface of water 
1 Phil. Trans., 1747. ® Ibid., 1747. 3 Tbid., 1751. 
