x The Preface. 



and regular feries of Experiments > which 

 are the only folid foundation whence we 

 7nay reafonably expeEl to make any ad- 

 vance in the real knowledge of the nature 

 of things. 



I muft not omit here publiekly to ac- 

 knowledge ', that I have in fever al refpeSls 

 been much obliged to my late ingenious 

 and learned neighbour and friend Robert 

 Mather, of the Inner-Temple, Efq\for 

 his ajjijla?tce herein. 



Whereas fome complain, that they do not under- 

 fland the fignification of thofe fhort figns or 

 characters, which are here made ufe of in many 

 of the calculations, and which are ufual in 

 Algebra ; this mark -f- fignifies more, or to be 

 added to. Thus page 18, line 4, 6 ounces -(- 240 

 grains, is as much as to fay, 6 ounces more by, 

 or to be added to 240 grains. And in line 16, 

 of the fame page, this mark x or crofs figni- 

 rles multiplied by ; the two fnort parallel lines 

 fignify equal to -, thus 1820 x 4= 7280 : 1, is 

 as much as to fay, 18 20 multiplied by 4 equal to 

 7280 is to 1. 



THE 



