72 The Evolution of Floating and Other Dry Docks. 



3. It can be removed at a nominal cost should re-arrange- 

 ment of the harbour be facihtated thereby. 



4. The largest can be constructed in less than 12 months with 

 certainty, from the signing of the order. 



5. It can be extended from time to time at a cost per ton 

 about the same as the original structure, and need not be a day 

 out of commission. 



6. It is a most valuable asset, as it can be sold and towed to 

 its new home with ease and little expense. 



7. It may be moved out to sea to a vessel unable to come 

 into Harbour, and carry both itself and burden up the channel 

 for repairs. 



8. In case of war it can be taken to the base of operation and be 

 equally as effective in any sheltered harbour as Belfast. 



9. It can adopt itself to any list a damaged or sinking vessel 

 may have that would debar a large vessel from entering even 

 the largest graving docks yet made. 



10. All round it is more accurate, safe, and labour saving 

 than a graving dock, and as now made, quite capable of 

 reducing the time for docking and undocking by one half. 



1 1. The process of drying the vessel is accelerated consideiably 

 by the fact of having open ends aud being on a level with the 

 water instead of down in a deep hole, away from the mfiuence 

 of air currents or the sun. 



12. It can be constructed locally. 



For purposes of comparison I shew side by side two sections, 

 one representing the most modern graving dock yet constructed 

 and the other the most modern floating dock ; the graving 

 dock can only take in a vessel drawing 27 feet on the average 

 spring tides, whilst the latter can take one drawing 34 feet on 

 either spring or neap tides. 



Graving Dock, Floating Dock. 



Weight of structure ... ... 84,650 6,500 



Time in construction ... ... 6^ years. i year. 



Cost, about ... ... v.. :^35o,ooo ^125,000 



