ALUMINIUM. 211 



presenting to me the knowledge of a fact in a tangible, con- 

 crete form. 



So, having justified in your eyes, as I would fain hope, my 

 partiality for rough corporeal demonstrations leaving as little 

 for the imagination to supply as may conveniently be do me 

 the favour to take from yonder dust-heap a brick. I am not 

 particular about the sort of brick ; any sort will do. You 

 cannot find a brick ; good, that broken tobacco-pipe will per- 

 fectly answer my wishes. 



Having withdrawn the broken tobacco-pipe from the seem- 

 ingly ignoble materials of a dust-heap having attentively 

 regarded it as to weight and size suppose I tell you this, 

 that from the very tobacco-pipe shank you there hold in your 

 hand that coarse, ugly tobacco-pipe the chemist can ex- 

 tract a lump of beautiful white metal, more resplendent than 

 silver, more unalterable than silver when exposed to air, more 

 musically sonorous than bell metal ; ductile, laminable, fusi- 

 ble, and tough; then what will you say? 



Suppose that, proceeding, I furthermore tell you that 

 the metal in question does not exist in the material of the 

 tobacco-pipe in a mere minute proportion, but that when 

 extracted it will occupy something about two-thirds the bulk 

 of the tobacco-pipe itself; that in addition to its being the 

 chief constituent of all clays, it exists still more largely as 

 to percentage quantity in the ruby, the sapphire, corundum, 

 and adamantine spar ; you may believe me I think you will 

 but, naturally enough, you want proof. 



A tobacco-pipe is composed of baked, or more correctly 

 speaking bumtj white clay. Practically we may regard all 

 clays as identical in composition. Some contain mineral 

 colouring matters, especially iron oxide, or rust, and this is 

 the reason why building bricks are red, whilst others, like 

 pipe-clay, are devoid of colouring matters. Practically, how- 

 ever, we may regard all clays as identical in composition. 



To illustrate this subject by reference to brick, one might 



