96 IMPRO VED FISHER Y HARBO UR A CCOMMODA TION 



by oaken treenails, but were also cut so as to dovetail into 

 each other, and thus to render the mass practically 

 monolithic. They were also further secured by vertical 

 wedges." Such expensive methods are manifestly only 

 warrantable in peculiar works, where any uprooting of a 

 portion might indefinitely prolong the undertaking. 



CONCRETE OR BETON. 



This material has quite revolutionised harbour building, 

 and is coming into increased use yearly. Its use has 

 already been adverted to, but it is so fast taking the place 

 of stone that some further space must be devoted to it. 



Mr. Stevenson mentions it as having been introduced 

 by Mr. Walker from France as a substitute for backing. 

 Cast in huge blocks, in boxes with moveable sides and tops, 

 it is of almost ubiquitous use in harbour-wall foundations ; 

 in France, and at the entrance of the Suez Canal, and 

 elsewhere, they have been placed in the water without more 

 special arrangement than pierres perdues, and allowed to 

 take their own positions on the line of work. Huge 

 artificial monoliths are constructed thus, and, by plank 

 arrangements, continuous building has been successfully 

 carried out. 



Mr. Stevenson particularly mentions works carried out 

 by Mr. Balmer, Port Gordon, by putting a saw-draft in 

 each plank, and placing thin plates of iron between them, 

 thus forming a continuous mould for the concrete. 



This method finds increasing favour, and on account 

 of the facility of manipulation it will probably always 

 continue so to do. 



The quarrying of huge stones is thus avoided, and 

 the splinters or spawls are worked up with the greatest 



