A correspondent writing to the New York World from Scranton, Pa., states that a loss of at least 20 per cent of coal results from breaking the lumps in small pieces for domestic use, and that the dross or cu/m, as it is called, is a per fe c t incumbrance at the m i n es and large coal ya rd s. The consumers a c tual ly pay for thi s loss, as the l u m p coal is usu al ly sold for about fifty c e n ts less per tun than the broken screened sizes. He states that if persons w o ul d p u rc hase their coal in l u m p size, and have it broken themselves with hammers, they would find th a t one tun of it w oul d go as far as a tun an d a q u a r ter of the pre pare d sizes. W i th the loss sus-ta i n ed in blas ti ng coal in the m i ne s, and by bre ak i ng th e lu m p s in m ac h ines, we believe, only about 75 per cent of the e nt i re coal mi ned is u ti li zed. This is cert ainly an immense loss. One will see at any of the colleries of several years' standing in Pennsylvania hundreds of thousands of tuns of the was te coal standing in py ram ids, a n d considered worthless. The question is now asked: is there no way t o save this v aluabl e fuel? Here is ach an ce for inventors. The people will not take the trouble to p u rc h ase lump co al and bre.ak it up; t h ey rather pay more for the scree n ed and assorted vari e ti es p re pare d for their stoves, heaters and grates. But we believe the culm or dross may be presse d into blocks in m ach i nes, a nd thus m ade p o rtab l c. 11 c an c er ta i nl y be empl oye d for fuel in steam boa ts, and in the furnaces of steam boi le rs. We hav e no d o u U t but t h a t the mst piles of coal d us t n ow s ta n d i n g at th e colleries m.ay be c on verted i n to useful burning fu e 1, and, instead of being an i n -cumbrance, it may be rendered profitnble to mine owners. Arti fi c i al fu e l is n o w m ade i n E n gl an d from coal dross combined with a s mal l amount of adhesive substance, such as coal tar, and it is used on long voyages by m any of t h e best steamships. T h i s artificial fuel is pressed into bl ocks, and is well a d ap te d for packing in the coal bunkers of v essels. It is our opi ni on that the owners of mines in Pennsylvania may profit by the example . EXTENSION OF MCCORMICK'S TEN PATENTS.Application has been made to the Commissioner of Patents to extend the ten patents of Mr. Cyrus H. McCormick, of Chicago, Illinois, for improvements in h arve sti n g machines. A pa ten t was gmnted to Mr. McCormick on the 23d of October, 1847, which was surrendered and re-i ssned on M ay 24th, 1853, aga i n on the 21st of December, 18o8, and then again on the 20th of S e p te m ber, 1859, w h en it was r e-i ss u e if, divided into ten pate nts, n u m b e red re s pec t i vely from 816 np to 825, incln sive. The expiration of the oi'iginal patent term will take place on the 23d of October, 1861. The tetim ony in this case will be closed on the 28th of January next, an d the day of h eari ng before the Commissioner is s et down for the 11th of next February at 12 o'clock.