430 Proceedings. 



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 JVeivs, 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 Prance, 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 

 haH 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 Eansome'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 

 G-eological Survey of ISTew 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. 



