114 MACHINE FOR RAISING COALS OR ORE. 



of right cones, at 24 inches radius. Again, as the descending; 

 part of a chain 4- a basket of coal of double its weig-ht, un- 

 bending out of equidistant grooves from the base of a frus- 

 tum of a right cone towards its smaller pei'imeter, balances 

 in every revolution of the barrel a chain of equal weight 4- 

 a basket of coal of double its weight, bendaig into equidis- 

 tant grooves from the smaller perimeter of a similar frustum 

 towards its base, the counterpoise required must be equal in 

 all parts of the descent. 

 Maximum ©f So that by making the weiofht of the basket of coal to 



■ff •«■ J ts n 



that of the chain, aud the perimeters of the frustums of 

 cones, which form the barrel, to each other in the propoi*- 

 tion of two to one, a maximum is obtained, hy which a bar-- 

 rel of this description requires one third less 7nomentum, (and 

 consequently one third less expense), to work it than a cylin- 

 drical one. 

 Barrels. The barrels are made by nailing two or three inch planks 



upon wooden or iron curves, as in the common way; and af- 

 terward folded spirally with wrought iron tire, so as to leave 

 a vacancy of about half an inch between each fold, for the 

 lower part of the ellipses of those links of the chain which 

 work vertically to move in, and keep the coils at an equal 

 distance from each other. 

 Iron work. The wrought iron tire is of two kinds, the one for conical, 



and the other for cylindrical barrels; the cross section of 

 that for the barrel formed of frustums of cones is nearly a 

 parallelogram l| inch by ^ths; out of the upper part of 

 -which about one fourth of an ellipsis is taken, to form a ho- 

 rizontal bearing for those links of the chain, which lie flat 

 t\pon the tire; the cross section of the latter is a rectangle, 

 I5 inch by 2f inch. Both are rolled into their proper form, 

 and holes of a quarter of an inch diameter punched therein, 

 at a foot from each other, for the purpose of nailing them to 

 the planking of the barrels. 

 Chains work- As the method of working chains in grooves has only been 

 ^zfecQni'un^- ^" "^^ about three years and a half, it is impossible to give 

 tice. a certain idea in respect to their durability. In all that time 



not a single link has broke, or the least accident occurred 

 therefrom, though Messrs. T. W. and B. Botfield, have 

 nearly three thousand feet in daily motion at this manufac- 

 tory. 



