359 
THE OUTLINE OF CLOUD FOEMS : THE ELECTEIC 
CUMULUS, ANVIL CLOUD, AND EAIN-BALL. 
By SAMUEL BAKBER, E.M.S. 
B y the outHne of a cloud we most readily distinguish its class, 
and the peculiar characteristics it may happen to possess as 
a species. To take the case of Cumulus. Although the term 
Cumulus ” (a mass) does not indicate, so well as the names 
of the other two types adopted by Howard, the form which it 
presents to the eye, yet, in fact, the varieties of this cloud, 
which is of the utmost value in weather prediction, are, by 
outline alone, more distinctly defined and easier to be dis- 
criminated than those of any other. It would, perhaps, be 
possible to form a classification of the various species of the 
cloud entirely by their outlines. 
I distinguish four main varieties of cumulus, from which 
I select two forms, the most striking and the most valuable 
as weather prognostics, to illustrate the use of observing out- 
lines. The first is the Electric Cumulus,* and the second the 
Anvil Cloud of Sir J. Herschell. The outline of the Electric 
Cumulus is very sharp and hard, not broken by large indenta- 
tions, and loose feathery processes like that of the commoner 
kinds of cumulus, formed rapidly by exhalations from the 
earth, and drifting near its surface: but we have almost a 
continuous line, terminating perhaps in stratus or cumulo- 
nimbus below, yet rising to a vertex, conical or rounded, and 
consisting of a series of small curves and minute projections, 
representing the rounded protuberances on the surface of the 
cloud. 
There is no cloud that possesses a more distinct outline than 
this, and none which exhibits more brilliant or dazzling effects 
of light. As a weather prognosticator it is best observed at a 
distance, and near the horizon, when the form of the summit 
may be more exactly discerned. 
We now take the Anvil Cloud. 
* Previously described by me in the Quarterly Journal Brit. Meteor. 
Soc.,” Jan. 1872. 
