James Hutton (1726-1797)

II. The THEORY of RAIN. By JAMES HUTTON, M. D.
F. R. S. EDIN. and Member of the ROYAL ACADEMY of
AGRICULTURE at PARIS.

                                      PART I.

Invesligation of the Law of Nature, on which is to be founded a
Theory of Rain.

                    [Read by the Author, Feb. 2. 1784.]

 THERE is an atmospherical appearance which is not explain-
ed by the known laws of heat and cold. It is the breath
of animals becoming visible, in being expired into an atmo-
sphere which is cold or moist; and the transformation of trans-
parent stearn into fhe state of mist, when mixed with air which
is of a colder temperature. Natural philosophers have certainly
considered these appearances as being explained in the general
law by which heat and cold are communicated among contigu-
ous bodies, otherwise they would have endeavoured to point
out this particular law, which seems to depart from a more ge-
neral rule, or does not follow the natural course of things ob-
served on other occasions. The subject of this paper is to in-
vestigate a certain rule which, in the case now mentioned, may
be discovered as directing the action and effects of heat and
cold; and to form a theory of rain upon that investigated rule,
concerning the evaporation and condensation of water.

THE air, inspired by an animal, may be considered as a men-
struum dissolving water upon the warm and humid surface of
the lungs, and as thus becoming saturated with humidity in
this degree of heat. When this solution is again cooled, then,

                                                F

according