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other vapors, dilate themselves as they ascend, andconstouently are scattered through all the planetaryregions, and from thence are gathered up by thePlanets as they pass thro’ their Orbits, for they havea power to attract all bodies to them : Now thesevapours, bv entering into the atmosphere os theearth, m y well be supposed to contribute to therenovation os all things, and in particular to sup-ply the diminution caused in the humid parts ofthe earth by putrefaction and vegetation. So farare they from portending any mischief to us,which the natural fears of men are so apt to sug-gest, from the appearance of any thing strange oruncommon.

And that the tails of Comets have some suchimportant use is very reasonable, if we consider,that thele bodies seem to be framed of a texturewhich purposely disposes them to fume in that sort,and that they do not merely emit those fumes ortails by their near approach to the Sun alone with-out any other consideration ; for the earth is morethan half the year at a less distance from the Sunthan either of the two Comets were, which ap-peared in the years 1664 and 1665, when theywere nearest thereto; and the Comet of 1682never approached the Sun above half so near asMercury did, and but very little nearer than Venus ,yet all thole Comets emitted tails, whereas boththe Earth, Mercury and Venus were free from anysuch appearances.

The only objection that can be made againstthis opinion, is the difficulty of explaining how asufficient quantity of vapor can be raised from thebody of a Comet, to fill those vast spaces,through which their tails are sometimes extended.

Which