LET. VI.

Kepler and Galileo.

93

plants and animals which spring from the "bosomof the earth, to embellish it by their existence, andafterwards render back, by death, the fecunditythat nourished them.

That such extravagant dreams should be foundon the side of such sublime truths, is, as Mr.Voltaire observes, a matter not to be wonderedat; a man may be a great genius with regardto calculations and experiments, and yet makea wrong use of his reason in other respects.There are minds which stand in need of geometryto support them, and fall when they endeavourto proceed of themselves. It must be remem-bered, however, to the honour of Kepler, thathis errors were such as usually attend a quickand vigorous conception; and that some of hisconjectures were as grand and philosophical, asothers were whimsical and absurd.

His hypothesis for ascertaining the differentdensities of the fun and planets, according totheir distance from the center of motion, is aninstance of his penetration and judgment whichparticularly deserves to be mentioned. He con-ceived that the heaviest bodies in our system,must be those which are placed nearest the sun ;and as he was always desirous of rendering hisideas as familiar as possible, he illustrates themby the following easy example. The densityof Saturn may be compared to that of a dia-mond ; Jupiter to a loadstone; Mars to iron;

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