no

PlateXXVI.Fig. 6.

Hydraulics.

the Distances inversely, or of the apparent Dialv^ |of the Sun directly. !

37. For since the apparent Diameter A B of any y 'dy decreases with the Angle ACB under which h jj :seen, so that at C and D it will be as the Angles Aand A D B ; and these Angles decrease as their ,(or the Distances CF, DF) increase; it follows t * 1 ;the apparent Diameter A B is every where inversely *

the Distance, that is, at C or D we have A B as .jjf

or —^=. Whence if the apparent Diameter of theD r ^

be — D, and T S the Distance of the Sun, then I* 1 ’

D = and the Sun’s Force (F) to move the Se* ^(as strewn in Art. 9.) therefore F —

_-P 5 >

TS J . x - TS 3 " A

that is, the Force of the Luminary to move the Sea r'rreclly as the Cube of the apparent Diameter thereof. .

38. As the Force of the Moon to move the W* £ ^.

is at a Medium about 5 times greater than that of ^Sun, which is the tzssttts Part of Gravity ; that of £Moon will be the 7 ts< 58 Part of Gravity ; and th e£ ^fore by far too small to be sensible in the MotionPendulums, or any Kind of Static or Hydrostatic Fperiments. In the Motion of the Waters of the eonly can it produce any sensible Effect. . (

39. To estimate the Elevation of Waters whichEarth will produce in the Moon; let us suppose £Quantity of Matter (QJ in the Earth to be to th* £ 1the Moon (q) as 40 to 1, that is, Q_: q :: 40 : Jand let us first suppose the Earth and Moon ofBulk, and represented by AIK and B D E, and L

Fig. 7. Force (F) of the Earth, at the Surface of the Moon ’will be to the Force (f) of the Moon at the Sutf*.^of the Earth A, directly as the M a ff es of Mattel .each (because of the equal Distances T B and l>that is, F : f :: Q_; ^ 40 : 1. Again, let LB

L C as the Diameter of the Earth to that of the ^°° i0which is as 365 to 100, then will the Force at B /the Force at C as L B to L C, which let be as F to f