VI PREFACE. 



The popularity and success of the former 

 work have, as usual, called forth many la- 

 bourers into the same field. Some of these, 

 though borrowing from it with unsparing 

 hands, have thought proper to vary the form 

 of their instructions ; partly perhaps to con- 

 ceal that want of originality, which generally 

 enfeebles all compilations ; and partly to tempt 

 weak or sickly appetites, which have no pre- 

 vious taste for the invigorating food of real 

 knowledge. It is a commendable intention to 

 lure such triflers, by tales or dialogues, to more 

 solid reading, and more efficient instruction. 

 I mean not to discommend or undervalue any 

 of these humble attempts; but the subject 

 must not be reduced to their level. The only 

 radical fault in compilers, especially of ele- 

 mentary scientific instruction, is their inabi- 

 lity to appreciate what is most important to 

 teach or to enforce. « Hence they encumber 

 themselves, and alarm beginners, with loads 

 of unmeaning names, and of useless, or dis- 

 carded, terms. Let such be found in their 

 proper places, but not obtruded on the stu- 

 dent where they can render him no service. 

 The elements of every science are necessarily 

 dry enough ; but when they are correct and 



