or other Articles from Mines. 1 93 



long ; some have barrels formed of frustums of cones, 

 (whose perimeters are in the proportion of about five to four), 

 united ai iheir bases, and of various diameters; the axes of 

 both kinds are placed at right angles with the centre line of 

 the jiit, and at each end a rope of six inches in circum- 

 ference is n)ade fast by a staple, which ropes work (in con- 

 trary directions at the same time) over two pulleys, placed 

 in a frame parallel to each other, and at an equal distance 

 from the centre of the pit ; to the ends of these ropes the 

 baskets of coal and ore to be raised are hooked. 



The simplicity of their general structure is such as, per- 

 haps, not to admit of any considerable improvement ; but 

 the forms of the barrels are very defective. 



On [)utting one of these machines in motion each rope 

 forms a triangle, the lines thereof from the pulley to the 

 first and last coil, and the surface of the barrel, forming its 

 three sides. Upon the cylindrical barrel the load always 

 tends, from gravitation, towards the nearci;t point of con- 

 tact with the centre of motion of the barrel, and, in conse- 

 quence, the ascending rope at first bends around it in re- 

 ceding coils from the subtending side of the triangle, dimi- 

 nishing their distances as they approach the nearest point of 

 contact, (where the rope crosses the centres of the pulley 

 and barrel at right angles,) thereby leaving a great part of 

 the latter uncovered by the rope, and hence the necessity 

 of such long ones; afterwards coiling hard against itself as 

 it approaches the other side of the triangle, to its great in- 

 jury in wear. 



The barrels formed of Frustums of cones, united at their 

 bases, whose perimeters are in the proportion of about five 

 to four, are equally defective, on account of the rope, for 

 the reason before mentioned, binding hard against itself, 

 and even sometimes (in wet weather, when its rigidity is 

 increased by absorption of water,) folding at first in receding 

 coils, and afterwards so hard against itself as to force those 

 receding coils to slip suddenly towards the small perimeter 

 of tl)e cone, thereby making a large portion of the rope to 

 <lescend the pit in an instant, breaking the rope by the sud- 



Vol. 31. No. 123. Jug. 1808. N clen 



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