ON THE TOBACCO PIPE MANUFACTURE, ETC. 499 



This clay purified, absorbs moisture with extraordinary power. 

 Hence its use for removing grease spots from cloth and silk. As an 

 experiment take purified pipe-clay in powder, moisten with water, 

 powder sufficient to cover the grease spot the thickness of a shilling. 

 then break the head from off a long pipe, placing the thick end in 

 the fire until it is red hot, and placing the cool end in the mouth, 

 blow hot air on the moist clay, by which means the grease is softened, 

 and the water evaporated from the clay. The active evaporation 

 brings into play the powerful absorbing property of the clay, fo r 

 while the water passes off in steam, the grease takes its plaee. Remove 

 the clay when cold, and cleanse the material with a sponge. 



A remarkable and curious fact, illustrating the power of alumina, 

 or of aluminous clays (5,000 tons of which are used annually in New- 

 castle-on-Tyne in making alum), in the preservation of colour, may be 

 here related. In the year 1854, bunches of nuts were discovered 

 imbedded in the clay underneath the gravel at the Kingsteignton Pits, 

 twenty feet beneath the surface, in all their natural colours. 



Coruudrum and emery are alumina, without the use of which 

 substance grinding and polishing metals wotild be a diffiult process. 



Silicic acid is another principal constituent of most minerals and 

 next to oxygen, may be said to form the greatest portion of the earth's 

 crust. It is found in a variety of forms. Rock crystal, found in the 

 caverns of St. Gothard in beautiful hexagonal prisms, terminating in 

 pyramids with six faces, is pure silicic acid. In the soluble form it is 

 found in almost all springs, whence it enters into the organism of 

 plants, being as essential to the vegetable world as salt is to the animal 

 creation. It is not acid to the taste, and is endowed with very feeble 

 affinity ; hence it is sometimes called silica. 



Mica is the least important of the three chemicals enumerated as 

 composing granite, and it cannot be described by formula. Alumina 

 and silicic acid are the principal constituents. It is found in various 

 rocks largely distributed • for instance, in granite, gniess, and mica 

 slates, in which it is observable as lustrous laminae. It is found in 

 Siberia in large plates, which are used instead of glass for windows. 



Having endeavoured to describe the nature of pipe clay, we shall 

 now proceed to point out the various processes wdiich the pipe under- 

 goes prior to its completion ; and here there is much to interest and 

 much to admire. The pipe is an ingenious contrivance. The bowd is 

 a kind of furnace in which tobacco is burnt ; the chimney to this 

 furnace is a long or short perforated stem, and the draught is caused by 

 the smoker drawing air through the bowl ; this supplies the ignited 

 tobacco with fresh oxygen, and the products of combustion consisting 

 chiefly of nitrogen, carbonic acid, and oil of tobacco in a volatile form, 

 pass up the stem into the mouth of the smoker, the length of the stem 

 cooling the smoke, and owing to the porous nature of the clay, absorbing 



