OF THE FIGURE AND MOTION, &C.

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LETTER II.

Of the Figure and Motion of the Earth.

I N my last letter I have shewn you the ex-cellence and advantage of Astronomy ingeneral. I shall now come to particulars ; andendeavour to lead you, by gentle and easy steps,from the first principles of the science, to thoseparts which are the most interesting and useful.And as the earth we inhabit is constantly subjectto our observation, and is that with which weare the best acquainted, a description of its formand magnitude will naturally excite yourcuriosity and attention.

This vast body was long considered as a largecircular plane, spreading out on ail sides to auinfinite distance: and the heavens, above it,in which the fun, moon and stars appear tomove daily from east to west, were imagined tobe at no great distance from it, and to havebeen created solely for the use and ornament ofour earth. Of this notion are the vulgar, andthose who are ignorant of Astronomy, to thisday. But it is now well known to all mathe-maticians and philosophers, that the earth isC 2 of