a Portable Cofferdam. 147 



of rivers. The application of a double-framed waling, I have 

 also found in itself a very useful application in several situa- 

 tions, and for a variety of purposes. 



Report of the Committee of the Royal Scottish Society of Arts on Mr 

 Thomas Stevenson's Description of a Portable Cofferdam, for Marine 

 Puiposes. 



The Committee have carefully examined this description, with the 

 drawings and model, and are led to entertain a favourable opinion of the 

 design. The introduction of an internal and external frame of timber, 

 to retain the piles in their places, and guide the driving, is new, so far 

 as we know ; and with the simplicity of the construction, and the facility 

 with which the whole apparatus can be moved about, we have no doubt 

 it must prove a valuable auxiliary in the construction of Marine Works, 

 such as are described, where the depth of water is not great, and the bot- 

 tom rocky or irregular. Mr Stevenson states, that he has already ap- 

 plied it successfully in the foundation of a harbour-waU, and excavation 

 of a tide-bason ; and in many other similar cases we think it is likely to 

 prove highly serviceable. We are happy, therefore, in being able to re- 

 commend it to the attention and favourable consideration of the Society. 



Geo. Buchanan. 

 William Wightman. 



Edinburgh, 23d March 1848. 



