10 OUTLINES OF NATURAL PHILOSOPHY. 



c. Smooth surfaces may be made to cohere, by bring- 

 ing them very close to one another ; but, 



In general, cohesion cannot be produced between 

 two bodies but by the intervention of fluidity. 



d. Cohesion is not a general property of body ; it does 

 not belong to elastic fluids, which are kept together 

 by pressure or by gravity. 



c. Adhesion is sometimes distinguished from cohesion ; 

 the former being the force that connects the par- 

 ticles of liquids ; the latter that which connects the 

 particles of solids. They are no doubt modifications 

 of the same force. 



23. All bodies at the earth's surface, if left to 

 themselves, descend in straight lines towards that 

 surface. This tendency or disposition to fall is 

 called weight, 



a. The weight of a given body may be employed tec 

 measure the weights of all other bodies. 



24. The directions in which bodies fall in diffe- 

 rent places of the earth, tend nearly to the centre 

 of the earth. 



a. At points not very far from one another on the 

 surface, the directions in which bodies gravitate are 

 nearly parallel, the distance of the earth's centre be- 

 ing great in respect of the distance of the bodies from 

 one another. 



If the distance is a nautical mile, that is, 6075 feet 

 pearly, the angle made by the directions of gravity is 



one 



