NOMOS. 99 



What, then, is the attractive force which plays' so 

 important a part in the formation of these orbits ? Is 

 it that force of gravity which causes a stone to fall 

 to the earth ? This question is a natural question, 

 for the force is universal. It is this force which 

 draws the bucket to the bottom of the well, which 

 caps the mountain with clouds, and which steadies 

 the car of the aeronaut as it floats high above the 

 earth. Now this is a question which has been 

 answered by comparing the space through which a 

 stone falls to the earth in a given time, with the space 

 through which the heavenly bodies fall in the same 

 time from the tangents of their orbits. At the surface 

 of the earth, then, the stone is found to fall through 

 193 inches in the first second ; and what is this when 

 compared with the distance through which the moon 

 falls from the tangent of her orbit in the same time ? 

 On making the necessary calculations it is found 

 that the moon does not fall more than the '05 3 6th 

 part of a single inch in this time, and therefore the 

 attraction of the earth for the moon, as compared with 

 the attraction of the earth for the stone, is in the 

 ratio of 1930000 to 536, or 3600 to 1. In other 

 words, the attraction of the earth, thus measured, is 

 3600 times less at the the moon than upon its surface. 

 But this is as we might expect, if the attraction is 

 inversely proportional to the square of the distance, 

 for the distance of the moon from the centre of the 

 earth is 60 times the radius of the earth ; and thus, 

 if we divide 193 inches, or the space through which 

 the stone fell in the first second, by the square of 60, 

 namely 3600, we get the 0'0536th of an inch, which 



