330 Miscellaneous Intelligence, 



and entirely siliceous, the other granitic and mixed with hasalt ; 

 they were washed, digested in muriatic acid, again well washed 

 and dried at a temperature of 212°. June 12, 1822, two speci- 

 mens of mortar were made as follows : — 1. White sand 896 parts, 

 hydraulic lime fresh from the furnace 300 parts ; the two mixed 

 with water and in the usual manner in a glass vessel weighing 

 787 parts, gave, vessel and all, 2630 parts. The water therefore 

 weighed 6V7 parts, and the fresh mortar altogether 1843 parts. — 

 2. Granitic sand mixed with basalt 896 parts, lime same as above 

 300 parts ; the water used weighed 612^ parts, and the mortar 

 altogether 1808^ parts. 



These two mortars, placed in the most favourable circumstances, 

 had in 15 days lost 27 per cent of their weight. On the 4th Feb. 

 1824, nearly two years after their preparation, they were disin- 

 tegrated by muriatic acid. The sand of No. 1, washed, dried, and 

 weighed, equalled 892 parts ; the loss of -^^-^ was evidently due to 

 the second washing. The sand of No. 2, treated in the same way, 

 amounted only to 883. leaving a loss of -fL. This being considerable, 

 500 parts of the original sand were digested with muriatic acid 

 to imitate the action which had taken place during the disin- 

 tegration of the mortar, and it was found that in this way it lost 

 T^y part. Hence it may be concluded that the hydraulic lime did 

 not attack either of the varieties of sand. 



From these experiments M. Vicat concludes that the solidifi- 

 cation of mortar, containing hydraulic lime and common sand, is 

 not the result of a chemical combination. He admits at the same 

 time that the solidification cannot be accounted for by mere me- 

 chanical adhesion between the hydrosilicate of lime (in the lime 

 used) and the sand, i. e., a mere entanglement of asperities, "we 

 must therefore admit a molecular affinity without subsequent com- 

 bination ; and thus distinguish two species of adhesion, namely, 

 that which is purely mechanical, such as exists between plaster 

 and wood or stone, and intimate adhesion analogous to that which 

 connects most incrustations to the surface on which they have 

 slowly formed. 



With regard to the hydraulic mortar made from common lime 

 and puzzolana, M. Vicat thinks the results are very different, and 

 is at issue with M. Berthier on the subject. The induration of 

 these mortars he thinks cannot result from a simple adhesion 

 without subsequent combination ; for if combination do not take 

 place, the lime should retain its usual properties, such as solubi- 

 lity, causticity, <^c., and the consequence would be that all such 

 water cements immersed in a current would be rapidly decom- 

 posed, whereas this does not take place. He also quotes an ana- 

 lysis made by M. John of a terras hydraulic mortar which had 

 been immersed for four years, and in which was found water 24., 

 rains of quartz 33., silica in combination 8., lime with trace of 



