CONSISTENCY. 1 15 



gazer," and those who are contented with that, 

 have little chance of reading these pages, even 

 though ten times simpler than they are,) should 

 have accurate notions of the consistency of sub- 

 stances. It is that which the unaided senses 

 immediately observe ; and all the changes or phe- 

 nomena that take place in nature, are brought 

 about through the medium of the consistency of 

 bodies. Be the sensation what it may, taste, 

 odour, sound, colour, warmth, or resistance, still 

 it is in the consistency of the body that we find it 

 out; and after mere motion, which though in 

 conjunction with other agencies it often changes 

 the appearances of things, is nothing but change 

 of place (and place without substance cannot be 

 known at all), all our knowledge of action or 

 appearance in nature, is change of consistency. 



There may be changes of consistency brought 

 about by motion and resistance ; .and the motion 

 may be the result of any thing that can cause mo- 

 tion, and the resistance any thing that can oppose 

 motion. Thus bodies that are compressible may 

 be squeezed into less space by the gravitation of 

 heavy weights placed on them. Cheese is gene- 

 rally pressed in that way ; and smoothing irons 

 and mangles compress the linen by their weight. 

 A less compressible body being made to approach 

 a more compressible one very slowly, will squeeze 

 it together with far greater force than any weight 

 that is at all manageable. Screw -presses, which 

 are used for so many purposes, and Bramah's hy- 

 draulic or water-press, act on that principle. The 

 finer the threads of the screw are, the more power- 

 ful is the press ; and so, as there are no particles 

 or parts that the eye can find or the finger touch 



