Terrestrial magnetism did not acquire a right to be regarded
as a science until partial results were graphically connected in a system of
lines of 'equal declination, equal inclinatiion', and 'equal intensity'.
The term 'climate', taken in its most general sense, indicated all the
changes in the atmosphere which sensibly affect our organs, as temperature,
humidity, variations in the barometrical pressure, the calm state of the air
or the action of opposite winds, the amount of electric tension, the purity
of the atmosphere or its admixture with more or less noxious gaseous
exhalations, and, finally, the degree of ordinary transparency and clearness
of the sky, which is not only important with respect to the increased
radiation from the Earth, the organic development of plants, and the
ripening of fruits, but
p 318
also with reference to its influence on the feelings and mental condition of
men.
If the surface of the Earth consisted of one and the same homogeneous fluid
mass, or of strata of rock having the same color, density, smoothness, and
power of absorbing heat from the solar rays, and of radiating it in a
similar manner through the atmosphere, the isothermal, isotheral, and
isochimenal lines would all be parallel to the equator.
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