OF THE EARTH AS A MASS. 13 
of the composition and structure of the globe, mankind remained 
as ignorant as before . Wild, intricate, and tiresome romances, called 
Theories of the Earth, were published ; it was not till the middle 
of the last century that the rules of the inductive philosophy be- 
gan to be applied with any considerable degree of exactness to 
the speculations of Geologists, and it is only within a very few 
years, that the method of arriving at accurate conclusions in this 
science has been well understood. 
Valuable observations are scattered through writings of an ear- 
lier date, but they were neglected. It was between the years 
1775 and 1790 that Werner gave, at Freyburg, in Saxony, the 
new impulse to the study of Geology, which has resulted in all 
the recent improvements. In 1788, Dr. Hutton, of Edinburg, 
brought forward a rival theory, which immediately found zealous 
advocates and supporters, and thus furnished the kind of stimu- 
lus that was wanted to give interest to these investigations. — 
Since the latter date, there has been no want of industrious and 
ardent observers, and if in so vast a subject much remains doubt- 
ful and unsettled, it is nevertheless true, that the conclusions at 
which we have already arrived, are in the highest degree interest- 
ing and important. 
As affording a source of rational amusement and subjects for 
observation and study in after life, if on no higher ground, 
Geology and the different branches of Natural History, are en- 
titled to a place in a system of liberal education. They change 
the whole face of nature. No spot is more welcome to the eye 
of a botanist than a swamp or sand-hill, for there, are those plants 
of uncommon form and singular beauty which impartial Nature 
scatters with lavish hand over such localities, whilst she denies 
them to more genial soils. The more rugged and difficult a road 
is, the more interesting does it often become to the Geologist, for 
the strata are laid bare, and he can seethe composition, structure, 
and arrangement of the rocks. But we shall presently see that 
the science of Geology at least, claims our attention on far higher 
grounds than these. 
OF THE EARTH AS A MASS. 
5. Our knowledge of the great mass of the globe is very limit- 
ed, by reason of our inability to penetrate into its interior. The 
only particulars in relation to it that have been made the subject 
of inquiry and investigation, are, its form, density, temperature 
and composition. In regard to the two first, we may claim to 
have made some approaches to accuracy and certainty, but res- 
pecting the others, only to have formed conjectures of whose 
truth and correctness there is greater or less probability. 
6. Form of the Earth. — It is commonly spoken of as a sphere, 
and by those who would be more precise and exact, as a spheroid, 
having its equatorial about 26 miles greater than its polar diameter. 
2* 
