PREFACE. 



This work, in its original form, was published in the 

 Transactions of the New York State Agricultural So- 

 ciety for 1850, under the title of " Agricultural Dy- 

 namics," or the Science of Farm Forces. The present 

 edition is prepared on the basis of the original essay, 

 and is thoroughly revised and greatly enlarged, with 

 the addition of more than double the former number 

 of illustrations. 



It comprehends those branches of Natural Philoso- 

 phy known as Mechanics, Hydrodynamics, Pneumat- 

 ics, and Heat, in their more common application to the 

 practices of modern improved farming ; and, so far as 

 practicable, technical words and phrases have been 

 avoided, and the whole rendered simple and intelhgi- 

 ble to ordinary readers. 



The leading principles have been derived from the 

 existing stock of knowledge ; but no treatise on these 

 subjects, as specially applied to agriculture, having be- 

 fore appeared, the various examples of the application 

 of those principles to the structure and use of farm im- 

 plements, and to the farmer's daily routine, are mostly 

 original. 



For the purpose of adapting the work to schools, 

 wherever it may be desirable, it is divided into sec- 

 tions, each of sufficient length for a single recitation. 



