Leslie on Meteorology. 173 
be eminently advanced. Every man, and especially every Eng- 
lishman, is more or less a meteorologist ; often hazarding his 
property, comfort, and health, in his fancied proficiency. The 
morning salutation of friends has usually a reference to the 
weather, and is, in this island, generally followed by re- 
marks on atmospheric phenomena. The aspect of the sky 
is a never-failing topic of common-place conversation, and 
the evening farewell to society is frequently coupled with 
meteorological conjectures. Yet, notwithstanding all this inte- 
rest, attention, and observation of citizens, agriculturists, and 
sailors, joined to the speculations of the learned, meteorology 
cannot yet lay claim to the title of a science. Its phenomena 
are for the most part incoherent and anomalous; baffling very 
often the indications ofart, as well as the sagacity of experience; 
and its general facts are scanty in the extreme, or liable to nu- 
merous exceptions. Its very imperfection, however, gives a sa- 
lutary lesson, as it shews us in the clearest light, the inadequacy 
of the human faculties unaided by instruments of measure- 
ment and research, to explore the secret laws of nature. How 
instructive, in this respect, is the comparison of our knowledge 
of the heavenly bodies, with that of the atmosphere! The gra- 
duated quadrant and sphere soon enabled mankind to form some 
tolerably correct notions of the celestial movements ; nor can 
we, at the present day, think of the astronomical attainments of 
Hipparchus, and the masters of the Alexandrian school, without 
admiration. While the heavens have in these latter days, been 
unveiled in all the magnificence of their mechanism, rendering 
astronomy at once the lofty monument and hallowed sanctuary 
of human reason, the atmosphere continues a mere object 
of vague remark. It is but lately indeed that its phenomena 
have been at all subjected to instrumental examination. Torricelli 
and Sanctorio furnished the first means of measuring the varia- 
tions of its pressure and temperature ; circumstances now rigo- 
rously determined by the barometers and thermometers of mo- 
dern artists. Its electrical changes, so brilliant, but often so 
appalling to the common mind, were happily explored by the 
intrepid sagacity of Franklin, who traced out to succeeding elec- 
tricians an interesting line of research, which however has been 
but sparingly pursued. 
For the first accurate principles on which its condition as to 
moisture might be estimated, we are indebted to M. Le Roi, of 
Montpellier. He exposed a glass vessel containing cold water 
to the open air, and noted the highest point of temperature, at 
which the vessel possessed the power of condensing atmosphe- 
ric dew, onits sides. The nearer this point approached to the 
temperature of the atmosphere, the nearer the air approached to 
a state of aqueous saturation. Mr. Dalton has since rendered 
this simple fact subservient to the more refined purpose of mea- 
