FOR GREA T BRITAIN AND IRELAND. 99 



rocky bottom, so as to equalise it and render its surface 

 ready for founding on." 



"If this substitute for mortar and cement in rubble 

 and ashlar work be found capable of resisting the chemi- 

 cal action of sea-water, it bids fair to become of very 

 great value in sea- works." Mr. T. Stevenson's work having 

 been published as long since as 1864, further expe- 

 rience doubtless enables him to speak decidedly an this 

 material. 



MR. BREMNER'S PONTOONS. 



The proposal to construct in some adjoining place of 

 shelter, enormous pontoons of timber, for putting in the foun- 

 dation of low-water piers, the writer imagines must have 

 occurred to engineers in more than one instance. 



It has occurred to the writer of this in the case of a 

 proposed harbour many years since, where the bottom was 

 smooth and regular, and consequently fit to receive such a 

 pontoon. 



The under parts of the work are to be built in these 

 pontoons, which are to be towed by steam-tug from the 

 most convenient harbour in the vicinity for the construction 

 of such pontoons, to the desired spot, where they are to be 

 carefully grounded. Piles would have to be securely 

 driven to guide the pontoon into the required position, and 

 heavy anchors also laid down on each side of the site, to 

 assist in gaining it, and holding on the pontoon until it has 

 grounded as required. By valves arranged in the sides and 

 bottom, the water could be admitted so that the pontoon 

 could not again float. 



The whole of the foundation could be built of continuous 

 concrete by this method, and the superstructure could be 



H 2 



