226 MASSACHUSETTS AGRICULTURE. 



ing bite ; the resulting fragments will then fall lower down and 

 be broken again, and so on until they are made small enough to 

 pass out at the bottom. The readiness with which the hardest 

 stones yield at once to the influence of this gentle and quiet 

 movement and melt down into small fragments, surprises and 

 astonishes every one who witnesses the operation of the machine. 



It will be seen that the distance between the jaws at the bot- 

 tom, limits the size of the fragments. This distance, and conse- 

 quently the size of the fragments, may be regulated at pleasure. 

 A variation to the extent of f of an inch may be made by turn- 

 ing the screw-nut P, which raises or lowers the wedge Q, and 

 moves the toggle-block R, forward or back. Further variations 

 may be made by substituting for the toggles J, J, or either of 

 them, others that are longer or shorter ; extra toggles of differ- 

 ent lengths being furnished for this purpose. 



This machine may be made of any size. The builders have 

 patterns for several sizes, and are ready to make others as called 

 for. Each size will break any stone, one end of which can be 

 entered into the opening between the jaws at the top. The size 

 of the machine is designated by the size of this opening ; thus, 

 if the width of the jaws be ten inches, and the distance between 

 them at the top five inches, we call the size ten by five. 



The product of these machines per hour, in cubic yards of 

 fragments, will vary considerably with the character of the stone 

 broken. Stone that is granular in its fracture, like granite and 

 most kinds of sandstone, will pass through more rapidly than 

 that which is more compact in its structure. The kind of stone 

 being the same, the product per hour will be in proportion to 

 the width of the jaws, the distance between them at jthe bottom 

 and the speed. The proper speed is about one hundred and 

 eighty revolutions per minute ; and to make good road metal 

 from hard compact stone, the jaws should be set from 1^ to 1^ 

 inches apart at the bottom. For softer and for granular stones, 

 they may be set wider. 



The following table shows the several sizes of machines for 

 which patterns are on hand, — the product per hour of each size, 

 of fine road metal from the hardest materials when run with a 

 speed of one hundred and eighty, — the power required to per- 

 form this duty, the whole weight of each size, in round num- 



