Mr Rowell on the Phenomena of Evaporation. 51 
. Temperature . -, | Expansion of Water 
Heights. arAGe Density of Air. to Float. 
Level of the sea,..... + 60° i 860 
0°7943 1083 
0°6309 1363 
0:5011 1716 
0:3981 2160 
0:3163 2719 
Expansion of steam at 212° is 1800 times. 
Five miles is far above the usual height of clouds, but we 
have undoubted authority that clouds are sometimes seen at 
that height. But even at three miles high, the expansion 
of vapour to float must be 1716 times (very near the expan- 
sion of steam from boiling water), and the temperature re- 
duced to 23° below the freezing point. This, I believe, will 
be sufficient proof that the ascent and suspension of vapour, 
at such heights, must be caused by some agent, which is un- 
influenced by heat or cold. 
The hypothesis I offer on the subject is, that when ex- 
panded by heat, the increase of the surface of particles of 
water giving them a greater capacity for electricity, they 
are buoyed up into the air by their coating of electricity ; 
that if condensed near the earth’s surface, the extra-quan- 
tity of electricity is withdrawn, and the vapour falls as dew, 
&e. ; but if it rises out of the electrical attraction of the earth, 
and is then condensed, the electricity being insulated, forms 
an atmosphere around each particle of vapour, which sur- 
charge of electricity not only suspends the vapour by its 
lightness, but also repels the neighbouring particles of va- 
pour, and prevents the formation of rain; and on the re- 
moval (by any cause) of the electricity inclosing the vapour- 
ous particles, the repulsion* is removed, and the particles 
attract each other, and form rain. 
* In using the term repulsion, IJ mean that the particles repel each 
other to the extent of their electrical coating, and no farther : that bodies 
