310 



CALCAREOUS MANURES— APPENDIX 



uprights are further secured by cross pieces connected with the braces, and bearing in 

 front and rear of tlie wheel two steps on which the men stand as they go on or oti'the 

 wheel. 



w. Tlie wheel 4 feet in diameter, ihe steps S.^, feet lon^ 8 inches wide, made of IJ inch 

 plank. The ends of the wheels are formed of two tliicknesses ot incli plank placed 

 crosswise, the inside beim;: grooved to receive the steps which are placed about 8 

 inches apart. The axle of the wheei is 10 leel G inches long and S inches in diameter, 

 the portion around which the chain winds iseulnrgfd, so as to suit the lorce employed 

 on the wheel, or the weight to be raised, by nailing on strips of plank, over which a 

 few turns of old rope may be placed to prevent the slipping of the chain. 



To prevent confusion, only one crane (or arm) is represented in thia figure. 



The crane post is represented as turning on two iron pivots in pieces s, s, one bolted to 

 the principal post c, and the other spiked to the base. The crane post is 6 inches 

 square. 



a. The crane jib, 7 feet 6 inches long 6 by 7 inches. 



b. The strut to the jib, S feet 6 inches long 4 by (> niches. Near the extremity of the 

 jib an iron sheeve is fixed over which the chain passes. 



c. Is a three-quarter inch rod of iron secured to a by means of a staple, and having a 

 hook at the other end which drops into a staple at i. This rod serves the double pur- 

 pose of a stay and a guide, by which (when unhooked; the arm is drawn to one side 

 for the purpose of landing the box. When fixed, as represented in the drawing, it 

 serves to retain the crane in its proper position. When the box is raised the rod is 

 unhooked, and by means of it the box is landed. 



Figure 2 is a front view, showing the relative position of the cranes, which are repre- 

 sented as turned aside. The chain is seen winding around the axle. It is evident 

 that the men must pass to the opposite side of the wheel as each box is drawn up. 



J, J. Represent 2 views of the boxes, which are square and may be each about 21 inches 

 every way, tliey will then contain nearly 6 cubic leot each. 'I'hey are sus[iended by 

 two pi;is plac(!d a little below and to one side of llie centre so as lo turn over and 

 empty themselves when a small iron ))in seen at_;, figure 2, is withdrawn. Three 

 men can be employed to advantag'! at the wheel, two lemaining on vvliiUt the third 

 gets off to land the box. 8hould the box not be heavy enough tlie diameter of the 

 axle can be enlarged so as to makeup in time what is lost in weight. Should it be too 

 heavy for the force employed the diameter may be lessened." 



The above dimensions of timbers were tliose of the particular machine 

 measured by Dr. Archer; but they vary in all the machines of this kind 

 used at the fortress. The length of the arms of course should be propor- 

 tioned to the height to whicli the loaded buckets are to be raised. For 

 mar], any sized timbers on hand, or logs, that are long enough, would serve 

 for the base (i, ;.) It is however desirable that the machine should be as 



