MECHANICS AND USEFUL ARTS. 113 



It is a stationary cylinder of wood, open on the top, ten feet long by six 

 feet in diameter, in which is a horizontal shaft, so secured that the inside 

 heads of the cylinder revolve with it ; and on these heads, extending across 

 near the periphery, are iron bars, varying in form, which have the duty of 

 mixing and thoroughly incorporating the flour and water as they revolve. 

 This part of the operation of kneading is the first in order after the sponge 

 is raised, and is performed by the rotation of the cylinder in a few minutes. 

 After this work is done, another operation commences, which is executed by 

 an additional cross-bar, which is movable and is inserted at the right time. 

 This is a plain plank-shaped affair, which swings on hinges in an eccentric 

 manner, and plunges into the dough at the bottom of the cylinder, cuts off 

 and raises up a portion of the dough till it passes over a certain point, 

 spreading and drawing it out in the act, and then throwing or flapping it 

 down with force, so as to inclose the air and imitate the same motion and 

 result accomplished by the workman with his hands and arms. This move- 

 ment is continued until the dough is perfectly kneaded, when it is taken out 

 by a trap-door, and the machine is ready to receive another batch. 



IMPROVED GAS-BURNERS. 



At a recent meeting of the Franklin Institute, Mr. S. S. Garrigues ex- 

 hibited specimens of bat-wing, fish-tail and Argand burners made of por- 

 celain, the object being to get rid of the rusting, which occurs in metallic 

 burners when exposed, thus preventing a perfect combustion of the gas. 



To obviate the corrosion, and expansion of the orifices of gas-burners by 

 heat, he has lately manufactured gas-burners from soapstone (steatite), which 

 is prepared for this purpose in a peculiar manner. This stone is cut up into 

 small four-sided slabs, put into hermetically sealed cases, and exposed to a 

 slow fire until it becomes red hot. Great care is exercised in thus roasting 

 the stone, because if quickly heated, it will rupture by the sudden expansion 

 of small particles of moisture in it. The steatite slabs are exposed to this 

 heat for about two hours, slowly cooled, and are then easily turned to the 

 proper shape in a lathe. After this they are boiled in oil until they acquire 

 a deep brown color, when they are taken out, dried, and made to assume a 

 beautiful polish by simply rubbing them with a woollen rag. The boring 

 of gas-burners is an art requiring great care and skill, as the opening of each 

 burner is formed to consume a certain quantity of gas. 



Gas-burners made as described from soapstone are stated to be perfectly 

 fire-proof, and not liable to any change or alteration in the size of the bore 

 or nature of the material by the strongest heat produced by the combustion 

 of the gas. Liebig gives these burners a very high character, and advises 

 all chemists to employ them in their laboratories, as they are not affected by 

 the largest flames to which they may be exposed in applying them to distil- 

 lation or other methods of analysis, etc. 



Batchdder's anti-flickering gas-burner attains its object by means of a circle 

 of minute jets of flame around the light. These create an ascending current 

 ' that shield it from the cool current as effectually as the glass chimney of the 

 common argand lamp. 



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