STUDY IX. 209 



Earih a fpinning round it's own axis. It may be 

 fo ; but if the Earth revolves round itfelf, there 

 muft be a great difference in the fpace pafled 

 through by two cannon-balls, fliot off at the fame 

 inftant, the one toward the Eaft, and the other to- 

 ward the Weft ; for the firft goes along with the 

 motion of the Earth, and the fécond goes in the 

 oppofite diredion. While both are flying in the 

 air, and removing the one from the other, each 

 proceeding at the rate of fix thoufand fathoms in 

 a minute, the Earth, during that fame minute, is 

 outflying the firft, and removing from the fécond, 

 with a velocity which carries it along at the rate 

 of fixteen thoufand fathoms j this ought to put 

 the point of departure twenty-two thoufand fa- 

 thom behind the ball which is flying to the Weft, 

 and ten thoufand fathom before that which is fly- 

 ing to the Eaft. 



I once propofed this difficulty to a very able 

 Aftronomer, who confidered it as almoft an infult. 

 He replied, as the cuftom of our Dodlors is, that 

 the objeélion had been made long before, and re- 

 folved. At length, as I intreated him to have com- 

 paflion on my ignorance, and to give me the folu- 

 tion, he retailed to me the pretended experiment, of 

 a ball dropped from the top of a (hip's maft, when 

 under fail, and which falls on deck clofe to the 

 rnaft, notwithftanding the fhip's progreffive mo- 



voL. ij. P tion. 



