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BOOK VIII. 



lower part is a palm wide and thick ; then gradually the upper part becomes 

 narrower and thinner, so that at the top it is three digits and a half wide and 

 two thick. It is bored through at the place where the angles have been 

 somewhat cut away ; the hole is three digits long and one wide, and is one 

 digit's distance from the top. There are some who make that part of the 

 head which is enclosed in the stem, barbed and grooved, in order that when 

 the hooks have been fixed into the stem and wedges fitted to the grooves, 

 it may remain tightly fixed, especially when it is also held with two quad- 

 rangular iron bands. Some divide the cam-shaft with a compass into six 

 sides, others into nine ; it is better for it to be divided into twelve sides, in 

 order that successively one side may contain a cam and the next be without one. 

 The water-wheel is entirely enclosed under a quadrangular box, in case 

 either the deep snows or ice in winter, or storms, may impede its running and 

 its turning around. The joints in the planks are stopped all around with 

 moss. The cover, however, has one opening, through which there passes 

 a race bringing down water which, dropping on the buckets of the wheel, 

 turns it round, and flows out again in the lower race under the box. The 

 spokes of the water-wheel are not infrequently mortised into the middle of 



. Box. ALTHOUGH THE UPPER PART is NOT OPEN, IT is SHOWN OPEN HERE, THAT THE 



WHEEL MAY BE SEEN. B WHEEL. C CAM-SHAFT. D STAMPS. 



