222 EENNIE'S DOCKS AND HARBOURS. PART VII. 



Everything being in readiness for commencing opera- 

 tions, the divers entered the bell and were cautiously 

 lowered to the place at which the building was to 

 proceed. A code of signals was established by which 

 the workmen could indicate, by striking the side of the 

 bell a certain number of strokes with a hammer, whether 

 they wished it to be moved upward, downward, or hori- 

 zontally ; and also to signal for the descent of materials 

 of any kind. By this means they were enabled, with 

 the assistance of the workmen above, to raise and lower, 

 and place in their proper bed, stones of the heaviest 

 description ; and by repeating the process from day to 

 day, and from week to week, the work was accomplished 

 with as much exactness and almost as much expedition 

 under water as though it had been carried on above 

 ground. 



Thus the entire repairs were completed by the 9th 

 of July, 1814 ; and to commemorate the ingenuity and 

 skill with which Mr. Eennie had overcome the extra- 

 ordinary difficulties of the undertaking, the trustees of 

 the harbour caused a memorial stone to be fixed in the 

 centre of the new pier-head, bearing a bronze plate, on 

 which were briefly recorded the facts above referred to, 

 and acknowledging the obligation of the trustees to their 

 engineer. They also presented him at a public enter- 

 tainment with a handsome piece of plate in commemora- 

 tion of the successful completion of the work. The 

 diving-bell, as thus improved by Mr. Rennie, has since 

 been extensively employed in similar works ; and 

 although detached divers, with apparatus attached to 

 them, are made use of in deep sea works, the simplicity, 

 economy, and expeditiousness of the plan invented by 

 Mr. Rennie, and afterwards improved by himself, con- 

 tinue to recommend it for adoption in all undertakings 

 of a similar character. 



