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[ 56 ] tion of water by air. I have given the reasons for this in my work, upon the modification of the at- mosphere; and shall only repeat here, that these mo- difications of the humor appear to me almost intirely to be produced by the igneous fluids ; and that if the air has any share in them, it is only as being an elastic fluid The particles of these fluids, each ac- cording to its degree of power, strike, separate, and draw along with them those of the humor, and com- municate to them the elasticity they possess; in the same manner as they do to the particles of all volatile, and likewise of at fixt substances which they cor- rode and decompose.

110. This system will not only furnish a solution of the paradox which engages our attention, but will, I believe, carry us much farther The heat of the fummer keeps the humor in very great agitation ; and though there is more: of the humor at this sea- son than in winter, yet this heat will not: allow it to continue either as long a time, or in as great a quantity, upon the bodies or in their pores. That is the reason why the hygrometer falls less. But we see at the same time, that the portion of the humor which does sojourn, and which I call the active part, has more power to dilatate the bodies, from the greater degree of motion impressed upon it by a greater heat. Consequently the dilatation of the bodies, from this cause, will be in a compound ratio of the quan- tity of humor, and of its active force, or of the heat. And if, for instance, we compare any summer's day, in which the hygrometer in open air is at the same degree u on any winter's day, the air on the sum- mer's day will contain more humor than on the winter's