DOVETAILING. 209 



a circle of about ninety feet in circumference. Instead, how- 

 ever, of merely laying the stones as is usually done, or even 

 letting them into holes cut in the rock, he hit upon a singularly 

 ingenious device, whereby the building was practically a single 

 stone. 



Instead of cutting the stones square or oblong, as is usually 

 done, he had them made so as to "dovetail" into each other, 

 much after the fashion of a child's puzzle toy, or the junctions 

 at the edge of a box. Thus, each stone fitted into those around 

 it, while the lowest tier was dovetailed in similar fashion into 

 the rock. 



The stone employed was that which is called Moorstone, a 

 very hard variety of granite. Each course of stones was care- 

 fully fitted together on shore, and their accuracy tested, and 



SUTUBES OF SKULL. SECTION OP DOVETAILED BOX. 



EDDYSTONE LIGHTHOUSE. 



they were then taken to the Eddystone rock, and fixed in their 

 places. Beside using these precautions, Smeaton fixed the 

 stones in their place with the strongest cement, and further- 

 more fastened the stones together and united the several courses 

 by strong oak treenails and iron clamps. As none of the stones 

 weighed less than a ton, and some of them were double that 

 weight, the strength of such an edifice may be imagined. 



The accompanying illustration shows the arrangement of 

 these dovetailed stones in one of the courses. It will be seen 

 that the central stone must be laid first, and then the others 

 arranged round it. The whole edifice is rather more than 

 eighty-five feet in height, so that the elements have every 

 chance of demolishing it, as they did that of Winstanley. 

 More than a hundred years have now passed since it was built, 



p 



