462 SEC. 12. APPLIED MECHANICS. 



a charger which rocks forward to the front of the furnace under the grate 

 bars, when, upon turning a crank, a central shaft carries the charger back 

 under a central opening in the grate, when a piston rises in the charger and 

 pushes the fuel up underneath the burning mass above. When the piston 

 rises level with the top surface of the charger, it is retained in place by a 

 catch until a reverse motion of the crank brings the charger again to the 

 front, when the catch releases the piston and the charger is again ready for 

 filling, the previous charge of fuel being sustained by a movable apron. The 

 grate is constructed to revolve, so that any melted coal or slag can be brought 

 to the door and removed quickly. 



By this method the ignition of the fresh coal is gradual, and the volatilized 

 coal, combustible gas, and carbonaceous matter pass from below through the 

 live coals above, and break at once into flame, and the greatest intensity of 

 heat is secured, and the gas and smoke consumed and a great saving effected. 



2216. Model of a Blast Furnace Boiler, upon elastic 

 supports. Jeremiah Head, M. Inst. C.E. 



Long plain cylinder boilers, when hung as ordinarily upon rigid supports, 

 are found to rise clear of the latter at their ends when in use, and in the 

 middle when out of use. This leads to seam rips, and frequently explosion. 

 By turning the small hand wheel right or left, it will be seen that, by the 

 method exhibited, the boiler is able to modify its form without straining, and 

 consequently without danger. 



2216a. Model of a portion of the Pontcysyllte Aqueduct, 

 which carries the Shropshire Union (late the Ellesmere) Canal 

 across the river Dee, and the Vale of Llangollen. G. R. Jebb. 



This model was made under the superintendence and direction of Telfords 

 before the aqueduct was built. . . . The aqueduct consists of 19 arches, 

 each having a span of 45 feet ; the total length is 1,007 feet, and the height 

 from the river Dee to the surface of the water in the canal is 127 feet. The 

 foundation stone was laid on the 25th July 1795, and the work was finished 

 in the year 1803. 



This model having fallen into partial decay was a short time ago restored 

 and repainted. 



2216b. Model of an Apparatus for Exchanging De- 

 spatches on Railways, without Stoppage of the Trains. 



M. Cacheleux, Paris. 



22 16c. Model of the late John Grantham's Patent Steani 

 Tramway Car. 



Also a detailed drawing of the above. 



Mrs. John Grantham, Croydon. 



2216d. Model Railway and Carriage, invented and made 

 by Richard Roberts, C.E., Manchester, in 1824, to illustrate the 

 nature of centrifugal force, in his lectures at the Manchester 

 Mechanics' Institution. A practical model. 



The Committee, Royal Museum, Peel Park, Salford. 



