32 ANNUAL OF SCIENTIFIC DISCOVERY. 



the fuel is converted into combustible gas, which may be applied 

 under most advantageous conditions." 



For burning fine coal we noticed a form of grate, a German con- 

 trivance, the u step-grate," formed of flat bars of iron, arranged with 

 the wide side uppermost, one above another, and with a certain space 

 between them. An inclined grate is thus constructed, through which 

 not even the finest coal can djrop, provided the bars are allowed suffi- 

 ciently to overlap, and yet there is ample space for the admission of air. 

 We have a conviction that these grates can be introduced with great 

 advantage in this country, especially with a view to the utilization of 

 fine coal refuse, and that they only require to be known to insure their 

 immediate and extensive adoption. Such grates are in pretty exten- 

 sive use in several localities on the continent of Europe, more particu- 

 larly for the consumption of lignite. In the south of France grates on 

 the ordinary principle, but composed of very narrow and deep bars 

 much nearer together than usual, are adopted with success in the case 

 of small coal impregnated with much iron pyrites. These bars are of 

 cast iron, one half-inch thick at the top, and only one quarter-inch at 

 the bottom, and five inches deep ; they are placed three-eighths of an 

 inch apart. We are informed that since this plan came into use the 

 bars of marine boilers in some cases where the coal is bad last three 

 times longer than previously. 



Siemens's Regenerative Furnace. This furnace, which has recently 

 excited great attention in Europe, was exhibited in model. Its prin- 

 ciple of construction we will endeavor to explain. Every one must 

 have been struck with the prodigious amount of heat which escapes up 

 the chimney, especially in furnaces where smoky flame may frequently 

 be seen issuing from the top. One great object of Siemens is to save 

 and transfer this heat back into the furnace ; and this is done in the 

 following manner : We assume that the reader has seen an ordinary 

 glass-house furnace, whether for the manufacture of flint, crown, Ger- 

 man sheet, or plate glass. Now, under or near such a furnace let there 

 be erected four distinct fire-brick chambers, each of which may be put 

 in connection with the interior of the furnace and the stack or chim- 

 ney. Let each chamber be filled with fire-bricks, piled much in the 

 same manner as bricks in a kiln, so that air may circulate everywhere 

 freely through the entire mass. We will designate these " regene- 

 rative chambers." Instead of directly using solid coal as fuel, we will 

 replace the ordinary fireplace by a large gas-generating furnace, not 

 like that which we have described above for burning peat, but con- 

 sisting simply of a chamber having a " step-grate," such as is above 

 described. The generator may be near, or at any convenient distance 

 from the furnace; and coal of a very inferior description may be 

 burnt in it. The conditions must be such that carbonic oxide and 

 combustible hydrocarbons may be generated, and conveyed through 

 flues into the interior of the furnace. Let us now suppose that two 

 of the regenerative chambers have been raised to a high temperature. 

 Instead of allowing our gaseous fuel to pass directly into the furnace, 

 we will cause it to traverse intermediately one of these heated cham- 

 bers, whereby its temperature will be greatly raised and that of the 

 chamber lowered in a corresponding degree ; and we will only admit 

 the air intended to support combustion through the other heated 



