AN ACCOUNT OP THE ' 



not be opened but by the hand of some ingenious 

 clock-maker, and not without a great deal of time 

 and trouble. 



After a good deal of thinking and calculation, 

 I found that I could contrive the wheel-work for 

 turning the planets in such a machine, and giving 

 them their progressive motions ; but should be 

 very well satisfied if I could make an orrery to 

 shew the motions of the earth and moon, and of 

 the sun round its axis. I then employed a turner 

 to make me a sufficient number of wheels and 

 axles, according to patterns which I gave him in 

 drawing: and after having cut the teeth in the 

 wheels by a knife, and put the whole together, I 

 found that it answered all my expectations. It 

 shewed the sun's motion round his axis, the diur- 

 nal and annual motions of the earth on its inclined 

 axis, which kept its parallelism in its whole course 

 round the sun; the motions and phases of the 

 moon, with the retrograde motion of the nodes of 

 her orbit; and consequently, all the variety of 

 seasons, the different lengths of days and nights, 

 the days of the new and full moons, and eclipses. 



When it was all completed, except the box that 

 covers the wheels, I shewed it to Mr. Mac Laurin, 

 who commended it in presence of a great many 

 young gentlemen who attended his lectures. He 

 desired me to read them a lecture on it, which I 

 did without any hesitation, seeing I had no reason 

 to be afraid of speaking before a great and good 

 man who was my friend. Soon after that, I sent 



