Leslie on Meteorology. 185 
distant:’”’);gives no absolute measure of the moisture of the air. 
In this respect it is on a level with the whale-bone slip of De 
Luc, and the hair of Saussure. But on Mr. Daniell’s plan, 
‘the difference between the constituent temperature of the 
vapour, and that of the air, gives a positive measure of the 
state of the weather, the probability of aqueous precipitation 
from the atmosphere being inversely to the magnitude of this 
difference.” Although the hygrometer of Mr. Daniell there- 
fore excels all others in sensibility, and in the accuracy with 
which it marks the comparative degrees of the moisture and 
dryness in the atmosphere ; and by exhibiting them in degrees 
of the common thermometer, refers them to a known standarc. 
of comparison, thus speaking a language which every body 
understands ; yet it is not upon this alone that its claims to 
superiority are founded. Its great merit consists in indicating, 
with ease and precision, the positive weight of aqueous gas, dif- 
fused through any given portion of space, and the force and 
elasticity of vapour, as measured by the column of mercury which 
it is capable of supporting. It may be also applied to indicate 
the force and quantity of evaporation. 
We now take our leave of Mr. Leslie, “ more in sorrow than 
in anger,” regretting that a philosopher of his acknowledged 
talents, holding, as he does, an eminent station in one of the 
first universities of Europe, and advantageously known to the 
scientific world by many interesting researches and ingenious 
inventions, should indulge in the whimsical speculations and 
strange vagaries contained in the subject of our Review. These 
“« quiddits and quillets” might possibly pass current in a meta- 
physical debating Society, but they ought not to have been 
published by the Professor of Natural Philosophy in the Univer- 
sity of Edinburgh. 
