CHAP. VTI. 



RAMSGATE HARBOUR. 



221 



backwards or forwards by means of a rack on the 

 frame, and a corresponding wheel provided with teeth, 

 worked by a handle and pinion. On the truck were 

 placed two powerful double-purchase crabs or windlasses, 

 one for working the diving-bell suspended from it, and 

 the other for lowering stone blocks or other materials 

 required for carrying on the operations at the bottom of 

 the sea. By these ingenious expedients the building 



METHOD OF USING THE DIVING-BELL. 



apparatus was so contrived as to move all round the new 

 work, backwards and forwards, upwards and downwards, 

 so that every part of the wall could be approached and 

 handled by the workmen, no matter at what depth, whilst 

 the engineer stationed on the pier-head above could at any 

 time ascertain, without descending, whether the builders 

 were proceeding in the right direction, as well as the 

 precise place at which they were at work. 



