EXPLANATION OF THE PLATES. Ixîx 



flronger one day and a half, or two days after the full 

 Moon, it is becaufe that Luminary increafes by her heat 

 the polar efFufions, and, confequently, the quantity of water 

 in the Ocean. The Moon poflefles a degree of heat which 

 not only evaporates water, as was afcertained by recent ex- 

 periments at Rome and at Paris, but which melts the ices, 

 as Pliny relates, in conformity to the obfervations of Anti- 

 quity. *' The Moon produces thaw, refolving all ices and 

 ** frofts by the humidity of her influence." Natural Hijlory, 

 Book ii. chap. loi. Finally, if the tides are more con- 

 fiderable at the Equinoxes than at the Solitices, it is be- 

 caufe, as has been obferved, at the Equinoxes, there is the 

 greateft poflible mafs of water in the Ocean, for the greateft 

 part of the ices of one of the Poles is then melted, and 

 îhofe of the oppofite Pole then begin to diffolve. 



We are not to imagine that every tide is a polar effufion 

 f)f the particular day when it happens ; but it is an effedl of 

 that feries of polar efFufions which perpetually fucceed to 

 each other ; fo that the tide which takes place to-day on 

 our coafls, is, perhaps, part of that which takes place, it 

 may be for fix weeks together ; and it's motion is kept up 

 by thofe which flow every day in it's feries. Thus in a row 

 of balls placed on a billiard table, the firfl: which receives 

 an impulfion, communicates it to the next, and that one to 

 the following, and fo through the whole feries, and the laft 

 only is detached from the row with what remains of the 

 moving force. But here, too, we mufl admire that other har- 

 mony which pervades the moft remote effedls of Nature : it is 

 this, that the evening and morning tides take place on our 

 coafts, as if they iffucd that very day from the higher and 

 lower part of our Hemifphere ; and that the tides of Sum- 



e 3 mer 



