August I, 1878] 



NATURE 





such a manner that they could be transported to their 

 permanent places without great difficulty. Level founda- 

 tions of concrete and stone were constructed on the fore- 

 shore, some of which were used to put together and rivet 

 the iron caissons forming the outer shell of the piers, 

 others to build the brick work for that part of the piers 

 between the river bottom and low water. 



Builditig and Floating the ()-feet 6-inch Cylinders. 



After the caissons had been put together and the brick- 

 work built in, they were floated between barges to the 

 point where they had finally to form part of the structure. 



The apparatus employed for lifting them consisted of 

 a system of iron girders resting on barges. Flat bars or 

 links having 2" holes 12" apart, connected the base of the 



Fig. 3. — Sinking of piers by compressed air. 



piers with hydraulic rams placed on these girders. The 

 weight could either be taken on the girders direct or on 

 the rams. At high water the girders were floated over 

 the top of the piers, and after the tide had receded, and 

 the base was accessible, the connection between the lifting 

 links and the base of the cylinder was made. As the tide 



rose again it lifted the barges, and with them the pier, 

 hanging between them off its resting-place, when it could 

 without difficulty be towed to its destination, where 

 previously moorings had been prepared for it. For this 

 operation it was of course necessary to have a tolerably 

 calm day, and as the weather in the Tay is subject to very 



