Page:Transactions and Proceedings of the New Zealand Institute - Volume 1 (2nd ed.).djvu/464

430 strength would obviate shaking by wind. (3.) If the flat roof be introduced, the leverage power exercised by the wind would be reduced to a minimum. (4.) The supply of sand and gravel is ample in and near the city. The required materials for the cement can be readily procured in unlimited quantities from the east coasts of this and of the Southern Island. Mr. Crawford cited the reports of the Commissioners on the Paris Exhibition, and articles in the Building News, in support of his statements, and also quoted from an article in the November number of the Fortnightly Review, entitled "The Future of London Architecture." The writer of this article states the concrete to be formed of gravel combined with hydraulic mortar and sand. According to experiments made in France, concrete formed with a proportion of five parts of cement to two of lime and thirty-six of sand, has an ultimate strength of four tons to the inch, being twice that of Portland stone, eight times that of Bath stone, and sixteen times that of brickwork, as determined by the experiments undertaken by the Institute of British Architects in 1863; and the cost of such concrete walling is only half that of brickwork.

The Secretary asked Mr. Crawford if he referred to the chemical or simply the mechanical process of making artificial stone? because he understood there was a chemical mode by which artificial stone was made, somewhat in the way in which natural stone is formed.

Mr. Crawford imagined that in the formation of any concrete for building purposes, the means used would be both mechanical and chemical. The concrete, however, the use of which he advocated, was not a chemical compound like Ransome's cement, but one of a much cheaper character, being composed of ordinary building materials, such as lime, sand, and gravel.

Mr. Sheath thought the principal question that would have to be considered was, whether buildings of concrete could be erected as cheaply as those of timber. The answer to this question would probably determine whether concrete would be brought into general use in this colony or not.

The Chairman asked whether the concrete had been tried in countries subject to earthquakes.

Mr. Crawford said he believed it had been principally used in Prance and England.

The Secretary read the following papers by Mr. Skey, Analyst to the Geological Survey of New Zealand, detailing some of the most interesting results of the work performed in the Colonial Laboratory during the last few weeks.

2. "On the Amount of Silver in Grold from Makara," by W. Skey.