AGRICULTURAL SUBSTANCES CARRY FORCE 2? 



of mechanics. Theoretical mathematicians and physicists 

 by their researches, and inventors, have given the basic 

 ideas for the development of practical mechanics. The 

 scientist and the practical man have alike contributed to 

 our sum of mechanical knowledge and to our collection 

 of mechanical appliances. 



Electricity deals with one form of the invisible force of 

 inorganic and organic substances which manifests itself 

 in many ways, and which is rendered active by some 

 molecular disturbance, as from friction, rupture, or chem- 

 ical action. The laws of the generation, storage, trans- 

 portation and use of this power and {he mechanical ap- 

 pliances driven by it furnish subject matter for school 

 studies and laboratory practice alike practical and useful 

 for mental training. 



Chemistry is that branch of the physical sciences which 

 treats of the minutiae of substances, as of their atoms, 

 their molecules, the relations these units sustain to each 

 other within substances with simple and compound 

 molecules and the manner in which molecules of dif- 

 ferent kinds are constructed. Theoretical chemistry 

 deals with the laws governing chemical action, while 

 applied chemistry treats of the relations of these laws to 

 agriculture, medicine, mining, sanitation, etc. Physics 

 and chemistry overlap or dovetail, as do all related 

 sciences, and classification cannot make straight lines 

 where nature has not made them. Classification, as in 

 books, is only to aid us in better organizing our 

 thoughts. 



Geology treats of the constitution and structure of the 

 earth, the operation of its physical forces, the history of 

 its development, including the causes and modes of 

 changes it has passed through, and the occurrence and 

 development of organisms. It embraces physical geog- 

 raphy in part, but is not concerned with political 

 geography. It includes a study of the successive layers 



