Polytechnic Association Proceedings: ggj 



and instantly the process of hardening commences. In a few min- 

 utes a quite hard stone is formed, indestructible in air, and the 

 common salt resulting at the same time is washed out. After a 

 thorough washing the substance is impermeable to water. The new 

 stone while in- the process of hardening, is thrown into a solution 

 of chloride of calcium, where it is boiled for some hours by means 

 of steam pipes passing through tanks. The process expels any air 

 that may have been imprisoned in the material, and doubtless 

 increases the energy of the chemical union. 



The material thus made retains precisely the fonn it received in 

 molding. It may, therefore, be worked into the most delicate pat- 

 terns while in the plastic state; thus elaborately wrought capitals or 

 other arcliitectural ornaments may be made with the same facility 

 that the plaster of paris is commonly used for copjang statuary. 

 In testing the strength of this concrete, it was found that blocks four 

 inches square, which had been made only ten days, required forty- 

 four tons pressure to crush them, while blocks of Bath stone of the 

 same size gave away under fourteen tons. Silicate of lime is not 

 very abundant in nature, although quite large deposits are found 

 in the northern part of the State of New York. 



CRYPTOPIA. 



This name has been given to a new alkaloid found in opium by 

 Messrs. T. and H. Smith, of London. The quantity found in opium 

 is very small. The discoverers obtained from four or five tons of 

 opium only five ounces of muriate of cryptopia. The primary 

 form of its crystals is a hexagonal prism. The new alkaloid con- 

 tains twenty-three equivalents of carbon, twenty-five of hydrogen, 

 one of nitrogen, and five of oxygen. 



LAGO MAGGIORE. 



The Italian journals continue to give accounts of land convul- 

 sions on the borders of this lake, as well as of the Lago di Garda. 

 Portions of the Tyrolean Alps have been for several months sub- 

 ject to periodical oscillations, which have kept the peasants in a 

 state of great apprehension. Some time ago a village near Lago 

 Maggiore was covered by an extensive landslide. Large masses of 

 rock and earth are continually falling from Monte Balbo, exciting 

 great consternation among the inhabitants of the valley. 



BAELOW'S PLANETARIUM. 



*In the Paris Exposition, Mr. M. Barlow, of Lexington, Kentucky, 

 IS exhibiting his ingenious planetarium, which is designed to give 



