204 M E M O I R S 0/ the 
{o that there can be no room left to doubt, but that this is the 
true caufc thereof. The Iprinp^-tides upon the new and full n^oons, 
and neap-tides on the quarters, are occafioned by the attraftive 
force of the fun in the new and the full confpiring with the at- 
traaion of the moon, and producing a tide by their united torces 5 
vvherc.:s in the quarters the fun raifes the water, where the moon 
depreffcs it, and on the contrary; fo that the tides are made only 
by the difference of their attraaions ; that the force of the lunis 
no greater in this cafe, proceeds from the very Imall proportion 
the femi-diameter of the earth bears to the vaft diftance of the 
fun. It is alfo obferved, that, cceteris paribus, the equinodtial 
fnrinptides in March and Sept. or near them, are the higheit, 
and the neap-tides the lowefl; which proceeds from the greater 
agitation of the waters, when the fluid fpheroid revolves about a 
rreater circle of the earth, than when it turns about in a leiier cir- 
cle: it being plain, that if the moon were conftituted m the pole, 
and flood there, that the fpheroid would have a fixed pofition, 
and that it would be always high-water under the poles, and 
low-water every where under the equinoaial ; and therefore the 
nearer the moon approaches the poles, the leis is the agitation ot 
the ocean, which is of all the greateft, when the nioon is in the 
equinoaial, or fartheft diftant from the poles 5 whence the lun 
and moon, being either conjoined or oppofite in the equinoctial, 
produce the greateft fpring tides, and the fublequent neap-tides, 
beina produced by the tropical moon in the quarters, are always 
the kaft tides ; whereas in June and Tiecember the Ipring-tides 
are made by the tropical fun and moon, and therefore Ids vigo- 
rous, and the neap-tides by the equinoaial moon, which there- 
fore are the ftronger; hence it happens, that the difterence be- 
tween the fpring and neap-tides in thele months is much Jels con- 
iiderable than in March and September. And the reaion why 
the very higheft fpring tides are found to be rather betorc the 
vernal, and after the autumnal equinox, viz. in February and 
OSiober^xh^n precilbly upon them, is, becaufe the lun is nearer 
the earth in the winter months, and lb comes to have a greater 
efiRfa in producing the tides. 
Hirherto we have confidered fuch affeaions of the tides as 
are univerfal, without relation to particular cafes; what 
follows from the different latitudes of places will c>e ealiiy 
under ftood by the figure. Let A/> EP, Fig. 4. Plate V 1. be 
the eavth, covered over with very deep waters; C its centre; 
Vp its 'Poles ; A E the EquimtVal; F/the parallel of latitude 
of a place, Dd another parallel at equal diftance on the other 
