MECHANICS AND USEFUL ARTS. 69 



ing power of the furnace, and the comparatively dense state of the air when 

 it mingles with the fuel. The combustion readily spreads upward to the fresh 

 coal from the action of the strong radiant heat. 



Gripper } s Smokeless Furnace. The principle of this recent (English) inven- 

 tion is that of mechanical motion applied to the bars, but different from any- 

 thing yet introduced. Every alternate bar is so connected with a cross-piece 

 at each end as to form one entire movable frame, which is connected by 

 gearing with the motive power. The motion given to it is angular ; first, the 

 bars rise very slowly about an inch above the stationary ones, they then 

 move gradually in a lateral direction toward the bridge, again sink in a verti- 

 cal direction about an inch below the other bars, and then move laterally for- 

 ward to their original position. What are termed the stationary bars are not 

 fixed as usual but hung in such a manner as exactly to balance the vibrating 

 frame with the load of fuel which it has to move, thus taking but little power 

 from the engine to keep them in motion. The fuel is fed through a hopper 

 and regulating incline plane, and the whole is self-acting, requiring but little 

 attention from the stoker. "We were informed that this apparatus has been 

 in constant use about six months, that no difficulties whatever arose from the 

 mechanical motion ; there was an entire absence of clinker, nearly perfect 

 combustion of the fuel was effected, and during our visit not a particle of 

 smoke was visible from the chimney. Mr. Gripper estimates the saving of 

 fuel alone at about 10 per cent., besides numerous other advantages. London 

 *R. JR. Journal. 



OX THE CONSUMPTION AND ECONOMY OF FUOEL. 



The following paper on this important subject, with the notice of some new 

 inventions connected therewith, was recently read before the London Society 

 of Arts, by the well-known physicist, Dr. Neil Arnott. 



Is it possible to avoid or to consume smoke in other words, to produce a 

 smokeless fire ? Common coal (bituminous) is known to consist of carbon and 

 bitumen or pitch, of which pitch again the elements are still chiefly carbon 

 and hydrogen, a substance which when separate, exists as an air or gas. 

 When the coal is heated to about 600 Fahrenheit, the bitumen or pitch 

 evaporates as a thick, visible smoke, which, when it afterward cools, assumes 

 the form of a black dust or flakes, called blacks or soot. If that pitch, how- 

 ever, be heated still more, as it is in the red-hot iron retorts of a gas work, or 

 in rising through a certain thickness of ignited coal hi an ordinary fire, it is in 

 great part resolved into invisible carburetted hydrogen gas, such as we burn 

 in street lamps. Now when fresh coal is thrown upon the top of a common 

 fire, part of it is soon heated to 600, and the bitumen of it evaporates as the 

 visible smoke, which immediately rises. If the pitchy vapor, however, be 

 heated to ignition by the contact of a flame, or of ignited coal near the surface, 

 it suddenly becomes hi great part gas, and itself burns as flame. This is the 

 phenomenon seen in the flickering and burning which takes place on the top 

 of a common fire. But if fresh coal, instead of being placed on the top of a 

 fire, where it unavoidably must emit visible pitchy vapor or smoke, be intro 



