190 REPORT—1849, 
and which upon passing the vapour-plane is immediately condensed. The 
supply continuing from below, and the condensation going on above, produce 
the heaping, piling-up, and general outline of the cloud—which is particularly 
characterized by its erenated edges, and to which it owes its picturesque ap- 
pearance—just as steam, which, issuing in an invisible state from the funnel 
of a locomotive, meets with a stratum of air sufficiently cold to condense it 
rapidly, by which it assumes in a very decided manner the characters of the 
highly-heaped cumular clouds. It has been suggested, that the immense 
masses of these clouds, so commonly met with in the calm latitudes between 
the trades, may possess some such an arrangement as above-mentioned—at 
least in the temperature of the rain that falls from them—by their more 
elevated portions being precipitated by the colder air with which they come 
in contact; and as it is likely the most elevated part of the cloud would 
most probably be situated near its centre, the precipitated rain would fall 
along the axis, and bring with it to a greater or less extent the temperature 
which contributed to its formation. The other portions of the cloud not 
being so elevated as the central would produce rain of a higher temperature, 
the rain falling from the skirts of the cloud being the warmest. 
One such cloud appears to have come under the writer's notice, at least if 
the difference in the precipitations may be regarded as indicating differences 
of temperature, or of elevation of certain portions of the cloud. The cloud 
was considered to extend over a diameter of about six miles; near the avis a 
fall ef snow occurred which was surrounded by a precipitation of hail, and 
from the portions near the shirts, rain fell. It would appear that the tempe- 
rature in the centre or axis was sufficiently low, or that the summit of the 
cloud was sufficiently elevated to freeze the vapour-particles before they had 
run into drops in the usual manner in which snow is formed; but in the 
zone characterized by the fall of hail, a different process appears to have 
contributed to its production. Upon the first formation of the drops, the 
temperature appears to have been above the freezing-point, and it is possible 
that the relative diminution of temperature in this zone might have been 
greater than in either the axis or skirts. If so, we have all the conditions for 
a very rapid formation of rain-drops, which, from their proximity to the snow 
‘ on the one hand, and the continued diminution of temperature on the other, 
might soon become frozen. There can be no question but that so rapid a 
conversion of aqueous vapour from the aériform to the solid state, must have 
been accompanied by electrical phzenomena more or less striking; the elec- 
trical condition of the cloud itself, as before observed, must have been mate- 
rially influenced, and this as it travelled onwards again influenced bodies in 
its more immediate neighbourhood as it passed them. In the observations 
more immediately before us, as well as in numerous others, we find that 
shortly after the rain began the charge became negative. That the cloud 
disturbed the usual electrical condition of the conductor is very evident from 
the observations, and it is to be presumed that, at the time the high positive 
charge was communicated to the conductor, the heavy rain was falling, 
although it had not arrived at the observatory ;—in other words, that portion 
of the cloud in which the diminution of temperature was so great as to occa- 
sion the rapid formation of rain, and thus alter the electrical condition of the 
cloud itself, was yet at some distance from the observatory. There might pos- 
sibly have been at this moment éwo bodies reciprocally acting on each other 
electrically—the body of falling rain and the cloud; and it may not be at all 
improbable that it is the actions of these bodies, the one on the other, that 
influence our conductors, and give rise to the sudden and extensive changes 
often recorded on the occurrence of squalls of rain, hail and snow. ‘The di- 

