OF THE TIDES. 



47 



H 



represent the earth, with its side c turned 

 towards the moon, which will then at- 

 tract the waters so, as to raise them 

 from c to g. But the question is, why 

 should they rise as high at that very time 

 on the opposite side, from a to e ? In or- 

 der to explain this, let there be a plate A B fixed upon 

 one end of the flat 

 bar D C ; with such 

 a circle drawn upon 

 it as abed (in the 

 preceding figure) to 

 represent the round 

 figure of the earth 

 and sea ; and such an ellipsis as e f g h to represent 

 the swelling of the tide at e and g, ocasioned by the 

 influence of the moon. Over this plate A B, let the 

 three ivory balls e f g, be hung by the silk lines 

 h i k, fastened to the tops of the crooked wires H I K , 

 in such a manner, that the ball at e may hang freely 

 over the side of the circle e. which is farthest from the 

 moon 3/(at the other end of the bar ;) the ball at/ may 

 hang freely over the center, and the ball at g hang over 

 the side of the circle g, which is nearest the moon. The 

 ball /may represent the center of the earth, the ball g 

 some water on the side next the moon, and the ball e 

 some water on the opposite side. On the back of the 

 moon M is fixed the short bar N parallel to the horizon, 

 and there are three holes in it above the little weights 

 p, q, r. A silk thread o is tied to the line k close above 

 the ball g, and passing by one side of the moon M, 

 goes through a hole in the bar N, and has the weight 

 p hung to it. Such another thread is tied to the line 

 t, close above the ball/, and passing through the center 

 of the moon M and middle of the bar N, has the 

 weight q hung to it, which is lighter than the weight 



