Lesson IV. J 



PHILOSOPHY. 



/'. -I will prove it to xpcri- 



eriiiK'nto'.] Take ,1 glass tube 

 (a, &,) with a bulb at the end (6); 

 let the bulb (6), and part of 

 the tube be filled with some 

 i of logwood, solution 

 of indigo, or other coloured 

 fluid, as far as c. Plunge the 

 bull) into hot water, and if you 

 observe, you will see the decoc- 

 tion of logwood, which is in this 

 tube, rapidly rising tow 

 because the fluid has dilated or 

 extended under the influence 

 of the increased temperature, 

 and is occupying a greater space 

 than before, therefore its volume 

 is increased. We will now allow 

 the fluid to cool, and you will *V * 

 observe that it will return to the level at c, 

 therefore we prove that the mass is the same 

 as before. If you repeat the experiment 

 with the bladder, [Experiment 1], you will 

 have another illustration of extensibility. 

 In both these experiments the elevation of 

 the temperature produces an incr 

 volume, which will be easily comprehended 

 by examining these two diagrams. 



C 



C. 



: 



* 



r,g. 4. 



5 represents a cubic inch of rold 

 ich we will suppose contains six- 

 teen atoms of nir, but v 

 same space only contains nine atoms, (as 





 the vo! > the size of 



but when the air again ' 

 it will return to the original size. i 



:nch of air contains the same 

 r of atom*, ii* the same 



as before. 



39. T. You have on ::ie two 



illustration*, the one relating to a fluid, 

 the other to a gaseous body. Can you 

 illus" v a solid bo 



P. \ 

 canter has become firmly fixed, s > 



cannot easily be withdrawn witln. 

 probability of breaking the decanter, if a 

 flannel is dipped into hot water, and applied 

 to the neck of the bottle, it will cause the 

 glass to expand [Experiment 7], and when 

 the neck is enlarged the stopper can be 

 easily extracted. 



40. T. Has the volume of a body any 

 relation to i 



/'. No. Bodies Inviiu? very different 

 volumes may have the same figure; and 

 bodies with different figures may havj the 

 same volume. Thus, a box may be ten 

 ia large as a die, or another box, 

 but yet have the same figure ; and a square 

 and a sphere may, though of dilferuit 

 figures, yet have equal volumes. 



41. T. Do you think that bodies can 

 be diminished in bulk, without diminishing 

 their mass 1 



P. Yes ; all bodies possess the property 

 of compressibility as well as extensibility. 



42. T. What do you mean by COM- 

 PRESSIBILITY ? 



P. It is that quality which all bodies 

 possess of having their volume diminished 

 without decreasing their 



43. T. Can you furnish me wit:: 

 familiar examples of the compressibility 



Of bod: 



P. The most elastic, and therefore the 

 most compressible bodies, si 



ml the most familiar of these is the 

 iieric air, which varies in bulk, ac- 

 cording as it is near or remote from the 

 earth's surface. It may appear v. i , 

 . tli.it tli hulk of the atm 

 should . 'is the case, 



and 1 will . xplain 



iagsof 



seed or flour, nn.l 

 placc tin : 

 above tin- 



i will easily 

 how 



those at th. 

 torn of the pile 



as those at tho 



top. 



illustrated by inrrn^n^ thr i. 



bags, urn! employing 1. It in 



on account : of the bap abovo 



ment. 



