18 FMILOSOPHICAL TRANSACTIONS. [aNNO 1665. 



The whole contrivance is farther illustrated by the following references to 

 fig. 2, pi. 1. Where, 



A, Is the hole for taking out the ashes. 



B, The square-hole, into which the tube or pipe for conveying the air is 

 fixed. 



C, The border or ledge, of brick or iron, on which the iron-grate or cradle, 

 that holds the burning coals, is to rest ; the one being exactly fitted for the 

 other. 



D, The hole where the cradle is set. 



E, The wooden tube, through which the air is conveyed to the cradle. 



F, The door, by which the grate or cradle is let in ; which is to be set eight 

 or ten feet higher than the hole D, the shutter being made of iron, or wood 

 that will not shrink, that it may shut very close. 



G, The grate or cradle, which is narrower below than above, that the ashes 

 may the more easily fall, and the air excite the fire ; the bottom being barred as* 

 the sides. 



H, The border or ledge of the cradle, that rests on the ledge C. 



I, Four chains of iron fastened to the four corners of the cradle, for taking 

 of it up, and letting it down. 



K, The chain of iron, to which the other chains are fastened. 



L, The pulley, of iron or brass, through which the chain passes. 



M, A hook, on which the end of the chain is fastened by a ring, the hook 

 being fixed in the side of the door. 



N, A bar of iron in the walls, to which the pulley is fastened. 



M. Du Son's Method of breahing RocJts. Communicated by Sir Robert 



Moray. N" 5, p. S2. 



The invention for breaking, with ease and dispatch, hard rocks is useful on 

 several occasions ; as in cutting adits, or passages through them, for draining 

 v^rater out of mines of lead, tin, or any other kind of minerals whatever. 



The mine or adit is to be made seven or eight feet high ; which though it seem 

 to make more work downwards, yet will be found necessary for making the 

 better dispatch, by rendering the invention more effectual. 



The tool employed in this operation is of iron, well steeled at the end, which 

 cuts the rock, of the shape in fig. 3, pi. 1, about 20 or 21 inches long, and 

 2^ inches diameter at the steeled end ; the rest being somewhat more slender. 

 The steeled end is so shaped, as makes it most apt to pierce the rock, the 

 angles at that end being always the more obtuse, as the rock is harder. This 

 tool being held by the hand, in the place where the hole is to be made, which 



