XlV ADVERTISEMENT. 



which he has treated. Besides the numerous altera- 

 tions which are to be met with in almost every 

 Lesson, he has added three New Lessons, one on 

 Electricity, one on Fountains or Springs, and one on 

 Plants and Vegetation. He humbly hopes that these 

 corrections and additions will ensure to him a con* 

 tinuation of that encouragement with which he ha* 

 Heen already honoured by an indulgent Public. 



Cambridge, 

 May 2<)th, 1799* 



Should any, who possess extensive philosophical 

 knowledge, honour this work with a perusal, they will 

 perceive that it is a juvenile production; being, 

 indeed, written originally before the author was 20 

 years of age : but, as its success has shewn its fitness 

 forjuveniTe minds, the Author should not think him- 

 self justifiable in making any alterations in the plan ; 

 but simply thinks himself bound to correct it as muck- 

 as possible, and to supply omissions by notes of refer- 

 ence, while the plan remains the same. The principal 

 additions and changes in the fourth edition, were in the 

 15th, imti, ( 24th, 28(A, 29th, and SQth Lessons. Sevc,- 

 ral minor corrections are made in thejlth edition. 



Ro} til Military Academy, 

 Aug. 20tii, 1815. 





