39 
other clouds in the neighbourhood, the phenomena might be 
complicated to any extent. 
And if, further, the motion of the sun is taken into 
account ; as the conductor S moves round E the charges in D 
and E would vary, accordingly as they were more or less 
between S and E and directly under the induction of S j 
i.e., the charge in a cloud would appear to change owing to 
the motion of the sun ; thus a cloud that appeared neutral 
at midday would, if it did not receive or give off any 
electricity, become charged positively in the evening. 
With regard to the independent motion of the clouds, 
there are several causes which would effect it. For instance, 
a cloud whether it appeared on the earth to be negatively 
or positively charged would always tend to follow the sun, 
though it is possible this tendency might be very slight. 
Again, one cloud would attract or repel another, according 
as they were charged with the opposite or the same electri- 
cities ; And in the same way a cloud would be attracted or 
repelled by a hill, according to the nature of their respective 
charges. 
Such, then, would be some of the more apparent pheno- 
mena under the assumed conditions. So far as I can see they 
agree well with the general appearance of what actually 
takes place, but as I have previously said, the laws relating 
to thunder storms are not sufficiently known to warrant 
me in doing more than suggesting this as a probable 
explanation. 
In these remarks I have said nothing whatever about 
what is called atmospheric electricity, or the apparent 
increase of positive tension as we proceed away from the 
surface of the earth. I do not think that this has much to 
do with thunder storms. If the law is established it seems 
