

CONSISTENCY. 123 



It is necessary that the observer of nature, if he 

 is to be any thing higher than a mere " unmeaning 

 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 imme- 

 diately observe ; and all the changes or phenomena 

 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 con- 

 sistency. 



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 generally 

 pressed in that way; and smoothing-irons and 

 mangles compress the linen by their weight. A less 

 compressible body being made ta approach a more 

 compressible one very slowly will squeeze it to- 

 gether with far greater force than any weight that 

 is at all manageable. Screw-presses, which are 

 used for so many purposes, and Bramah's hydraulic 

 or water-press, act on that principle. The finer the 

 threads of the screw are the more powerful is the 

 press ; and so, as there are no particles or parts that 

 the eye can find or the finger touch in water, so as 

 to take note of their magnitude, the column of water 

 which moves in the cylinder of Bramah's press is 



