BOOK VIII. 



A— Mortar. B— Upright posts, C— Cross-beams. D— Stamps. E— Their heads. 

 F — .4xLE (cam-shaft). G— Tooth of the stamp (tappet). H — Teeth of axle (cams). 



can remove with a shovel the fine sand, and hkewise the coarse sand and 

 broken rock, into which the rocks have been crushed ; this board can be 

 lowered, so that the mouth thus being closed, the fresh rock thrown in may 

 be crushed with the iron-shod stamps. If an oak block is not available, 

 two timbers are placed on the ground and joined together with iron clamps, 

 each of the timbers being six feet long, a foot wide, and a foot and a half thick. 

 Such depth as should be allowed to the mortar, is obtained by cutting out the 

 first beam to a width of three-quarters of a foot and to a length of two and a 

 third and one twenty-fourth of a foot. In the bottom of the part thus dug 

 out, there should be laid a very hard rock, a foot thick and three-quarters of a 

 foot wide ; about it, if any space remains, earth or sand should be filled in 

 and pounded. On the front, this bed rock is covered with a plank ; this 

 '•ock when it has been broken, should be taken away and replaced by 

 another. A smaller mortar having room for only three stamps may also be 

 made in the same manner. 



The stamp-stems are made of small square timbers nine feet long and 

 half a foot wide each way. The iron head of each is made in the following 



