MECHANICS 41 



As every one knows, solid bodies and liquid substances, 

 when unsupported, fall to the ground, such apparent 

 exceptions as balloons, <fcc., not being really exceptions 

 as will be seen later on. We say that bodies are " heavy," 

 and that it is their weight which makes them fall. But 

 this " weight " of theirs also causes them to press with 

 greater or less force, so to speak,* on whatever supports 

 them. Many things (intentionally or unintentionally) 

 are thus so pressed and squeezed that they become 

 flattened out thus making such pressure evident to 

 our senses. 



In this way it becomes plain that most (if not all) 

 things tend to fall, not only to the general surface of the 

 ground but as much deeper as circumstances may render 

 possible as water, stones, &c., will be sure to fall to 

 the bottom of the deepest excavation, unless arrested by 

 something which checks such fall and sustains the falling 

 bodies. We may then fairly assume that whatever tends 

 to fall, tends to fall towards the centre of the earth. 



Therefore everything on its surface which appears to 

 be (and for us practically is) in a state of rest, is really 

 tending to move and is only prevented from actually 

 moving by some other object which checks its progress. 



But we know that some things topple over very easily, 

 while others remain securely at rest. A die will lie 

 steadily on whichever side it falls, but if we heap a 

 number of dice upon each other, we shall soon erect such 



* The word "force" is now, in strictness, used to denote 

 the cause of motion, and "energy" to indicate the amount 

 of work a force can do. To enter here, however, into any 

 controversy as to the uses of such terms, would be foreign 

 to the purpose of a work which proposes only to introduce 

 students to the elements of science. We therefore do not 

 hesitate to employ a popular phraseology when it seems likely 

 to help on the purpose we have in view. 



