108 ANNUAL OF SCIENTIFIC DISCOVERY. 



required result, and thus forms a kind of thick paste, moulded readily 

 into any shape. Exposed for a time to the air, this gradually hardens 

 by the evaporation of part of the water, and when put into a kiln the 

 water is more rapidly and completely given off, the result being a per- 

 fectly solid mass, the original particles of sand being now cemented 

 together by a kind of glass, formed by the silicate of soda raised to a 

 red heat. The whole amount of water in any given quantity of the 

 unburnt stone does not exceed one-tenth part of its volume, but the 

 total amount of contraction is extremely small, and scarcely percepti- 

 ble in any case. On the other hand, the contraction in terra-cottas is 

 not only very considerable, requiring allowance to be made in mould- 

 ing, but is also extremely irregular. 



In consequence of the peculiarly simple composition of this new 

 material, it has been found easy to manufacture of it porous as well 

 as compact stone, and also such articles as grindstones and scythe- 

 stones (all of which enter into competition with natural stones) at a 

 considerable advantage, both in texture and price. The porous stones 

 are peculiarly useful as they make admirable niters, and by the simple 

 precaution of placing a coating of fine pure white sand upon them 

 they can never become choked. They are now extensively used, and 

 are found to succeed admirably. For pavements, balustrades, terrace 

 works, vases, and generally for all purposes of garden decoration, it 

 is well adapted by its cleanliness, sharpness of outline, color, dura- 

 bility, and cheapness. For ornamental flooring in halls, churches, and 

 public buildings, it possesses many advantages, and could be put down 

 at little more than half the price of encaustic tiles of similar patterns. 

 For quoins, cornices, battlements, chimney-pots, and many other 

 building purposes, it seems equally well adapted : while for niters it is 

 invaluable, and might be used to any extent in preference to any 

 known natural filter stones. London News. 



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PATENT OFFICE REPORT FOR 1852. 



The Patent Office Report for 1852, published during the latter part 

 of the year 1853, contains the following notices of several new inven- 

 tions, which have not heretofore been made generally public. 



New Reverberating Furnace. A novel form of reverberating fur- 

 nace, which is designed to dispense with the labor usually expended in 

 stirring and balling materials exposed to the action of the fire in this 

 species of furnace. A grate, fire chamber, ash-pit, &c., are, with the 

 fire bridge, constructed of brick in the ordinary manner ; and at the 

 usual distance therefrom is built a chimney and horizontal passage 

 leading into the same, also in the ordinary way. The body of the fur- 

 nace, the roof, and working bottom are omitted ; and their place is sup- 

 plied by a cylinder of cast-iron lined with fire-brick, and free to re- 

 volve upon metallic rollers. This cylinder has an area about equal to 

 that of the ordinary working chamber, is provided with a door fitted 

 like a man-hole or a hatch, and has revolution imparted to it by means 

 of a cog-wheel or a belt. The materials, broken pig for instance, are 



