MACHINES FOR CUTTING COAL IN MINES 157 



a crank handle, and thus a quick revolving motion can be given to the cutter, -whilst 

 that, at the same time, may be freely swept round to and fro in the arc of a circle. 

 Sloans are provided for the exclusion of dirt from the machinery, and ior holding the 

 apparatus securely while the cutter is in motion. An adjustment may be mailo for 

 cutting grooves, either vertically or horizon- ,,oi 



tally in the upper part of the seam, and in 



such case the spindle of the cutter is driven E A' J3' 



by a rotary engine set in motion by com- 

 pressed air. 



The mode of action of Mr. Jones's appara- 

 tus will be more clearly understood on refe- 

 rence to the diagram (Fig. 1421). The fixed 

 end of the cutter is supposed to be succes- 

 siA'ely at A, B, and c, the seam of coal lying g- 

 between the lines D D and E E. First the 

 cutter, starting from the position A A', travels 



round to the position A A", clearing the triangular space A A' A". Then the fixed end is 

 transferred from A to B, when a quarter revolution changes its direction from BB' to 

 B B", clearing the space B B' B", and on removal to the fixed point c, the similar 

 space c c'c" is cleared. 



Bidders Machine for breaking down Coal. Mr. S. P. Bidder, jun., had, in conjunc- 

 tion with Mr. John Jones, devised a machine which had been submitted to actual 

 trial on a working scale at the Harecastle Colliery, where the results were so satisfac- 

 tory as to induce the proprietors to make arrangements for its immediate adoption. 

 The machine consisted of a small hydraulic press of 12 tons power, to which was 

 attached a pair of tension-bars, bent in the form of a connecting rod or hinge-strap. 

 These were placed one over the other in the bore-hole, and between them, at the 

 extreme end, there were a clearance-box and two metal pressing-blocks, between which 

 was forced, by the action of the hydraulic press, a split wedge 15 inches long, causing 

 a lateral expansion of 3 inches. The ram was then withdrawn, and a second wedge 

 was inserted between the two parts of the first wedge, and was forced tip until suffi- 

 cient expansion was obtained to break the coal. The operation could be repeated 

 several times if found necessary. The whole apparatus would weigh about 50 Ibs. 

 The hydraulic press was in future to be made of steel, and the ram would be cored 

 out. In practical working, each gang of colliers would be provided with the tension- 

 bars and three wedges, while the presses would be under the charge of the men who 

 at present occupied the position of firemen, so that no new class of labour would be 

 introduced, while the risk of firing would be got rid of. Trials had been made both 

 in the 7-feet and the 9-feet seams at Harecastle ; and in the latter, with three wedges, 

 about 12 tons of coal had been brought down in only three or four pieces. It was 

 found that the press could be applied, and the blocks brought down, in less time than 

 was consumed by firing a hole and waiting for the smoke clearing. 



Explosions in mines were known to arise, very frequently, from the employment of 

 gunpowder for blasting. In the interests of humanity alone, an efficient substitute 

 had long been desired by practical men ; and this, it was believed, had been accom- 

 plished by Bidder's machine, which had also the advantage of preventing the waste of 

 coal incurred by the present system. 



The following remarks, made by Mr. W. Menelaus of Dowlais, on the use of coal- 

 cutting machines in the collieries of South Wales, are so much to the point that they 

 are extracted from the ' Journal of the Institution of Mechanical Engineers.' These 

 remarks have reference more especially to the coal-cutting machine of Mr. Eobert 

 Winstanley. 



Mr. Menelaus said that, having paid considerable attention to the subject of coal- 

 cutting by machinery, and watched carefully the several plans that had been tried, he 

 had not yet found any machine that could compete with colliers' labour under the 

 exceptional circumstances attending the working of the thick veins of coal in South 

 Wales. The holing of the coal constituted there only one-tenth of the entire labour 

 in the collieries ; and the margin for saving upon this portion of the work was there- 

 fore so small, that he had given up as hopeless the introduction of coal-cutting 

 machines in that district. The colliers at present worked only one turn of about 8 

 hours per day of 24 hours ; and the coal was all brought clown by natural pressure 

 during the interval while the men were all absent, the bulk of the coal being obtained 

 with very little holing. If three turns were worked per day he was not sure that the 

 holing might not be advantageously done by a machine, even in the thick soft veins of 

 the South Wales collieries; and in such a case, ho should be very glad to adopt 

 machines for the purpose. In thin veins of hard coal ho considered the introduction 

 of coal-cutting machines would be attended with very great advantages, and he hoped 



