Polytechnic Association. 683 



E. Bohmer and F. Neumann. Kalk, Gips unci Cement. Hand- 

 buch fur Anlage mid Betrieb von Kalkwerken, Gipsmtihlen und 

 Cementfabriken. (With atlas.) 1870. 



J. Mihalik. Die hydraulischen Kalke und Cemente ; ihre Verwen- 

 dung. (With five plates.) Pestli, 1870. 



G. Hagen. Handbuch der Wasserbankurst. Third edition. Ber- 

 lin, 1870. Consisting of several volumes and three atlases, with, 

 together, 123 plates in folio. 



The three following works form part of the reports of the United 

 States Commissioners to the Paris Universal Exposition, 1867, pub- 

 lished at Washington in the Government Printing Office, 1870 : 



Will P. Blake. Civil Engineering and Public Works. 



J. H. Bowen. Report upon buildings, building materials and 

 methods of building. 



L. F. Beckwith. Report on* Beton-Coignet ; its fabrication and 

 uses. 



Q. A. Gilmore. A Practical Treatise on Coignet-Beton and other 

 artificial stone. New York, 1871. 



Dr. A. Ott exhibited specimens of Frear stone, and of his own arti- 

 ficial stone. The latter costs about half as much as quarried stone, 

 and is relatively still cheaper for ornamental work, being as easily- 

 produced of any given form as cast iron. Frear stone now contains 

 Portland cement. 



The President said experiments by Dr. Calvert seem to show that no 

 real hydraulic cement could be formed without magnesia. However, 

 hydrated silicates are most essential. 



Dr. A. Ott considered magnesia unnecessary, the important ele- 

 ments being silicate of lime and silicate of alumina. 



Dr. L. Feuchtwanger said that the Frear stone had not stood the 

 test. Dr. Ott's cement was much better. 



The President stated that Frear stone contains shellac, an organic 

 substance, and therefore unlikely to be permanent. 



Dr. D. D. Parmelee said that unless the shellac were submitted to 

 heat, it would not be in the condition to form cement. Ransom's 

 stone has been found too porous for building stone, absorbing thirty 

 to thirty-five per cent of water. Any stone that will absorb fifteen 

 per cent of water is unfit for building in a climate where a heavy 

 rain is often followed by freezing weather. The pavements around 

 the New York City Hall look well now ; but the time to judge of 

 them will be after the disintegration from a winter's alternate freezing 

 and thawing has had its effect. 



