air and water be mov'd never so vehemently, as in high Winds and Cataracts, yet we are not to expect that they should be manifestly hot, because the vehemency belongs to the progressive motion of the whole body; notwithstanding which, the parts it consists of may not be near so much quickned in their motions made according to other determinations, as to become sensibly hot. And this Consideration may keep it from seeming strange, that in some cases, where the whole body, though rapidly moved, tends but one way, 'tis not by that swift motion perceived to be made Hot.
Nay, though the agitation be very various as well as vehement, there is yet a third Condition required to make it Calorific, namely, that the agitated particles, or at least the greatest number of them, be so minute as to be singly insensible. For though a heap of sand or dust it self were vehemently and confusedly agitated by a whirlwind, the bulk ofthe
