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Z O O N O M I A. 



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SECT. I. 



OF MOTION. 



THE whole of nature may be fuppofed to confift of two 

 effences or fubftances ; one of which may be termed 

 fpirit, and the other matter. The former of thefe poiTeffes the 

 power to commence or produce motion, and the latter to receive 

 and communicate it. So that motion, confidered as a caufe, im- 

 mediately precedes every effect ; and confidered as an effect, it 

 immediately fucceeds every caufe. And the laws of motion 

 therefore are the laws of nature. 



The motions of matter may be divided into two kinds, 

 primary and fecondary. The fecondary motions are thofe, which 

 are given to or received from other matter in motion. Their 

 laws have been fuccefsfully inveftigated by philofophers in their 

 treatifes on mechanic powers. Thefe motions are diltinguiihed 

 by this circumftance, that the velocity multiplied into the quan- 

 tity of matter of the body acted upon is equal to the velocity 

 multiplied into the quantity of matter of the acting body. 



The primary motions of matter may be divided into three 

 claffes, thofe belonging to gravitation, to chemiflry, and to life ; 

 and each clafs has its peculiar laws. Though thefe three claries 

 include the motions of folid, liquid, and aerial bodies \ there is 

 neverthelefs a fourth.. divifion of motions ; I mean thofe of the 

 fuppofed ethereal fluids of magnetifm, electricity, heat, and 

 light ; whofe properties are not fo well inveftigated as to be 

 claffed with fufficient accuracy. 



\Jl. The gravitating motions include the annual and diurnal 

 rotation of the earth and planets, the flux and reflux of the 

 ocean, the defcent of heavy bodies, and other phenomena of 

 gravitation. The unparalleled fagacity cf the great Newton 

 has deduced the laws of this clais of motions from the fimple 

 principle of the general attraction of matter : to fhould 



perhaps be a<j I te general repulfion of matter; whi. . fee 



Vol, T. B te 



