Polytechnic Association Proceedings. 653 



elevation of buildings. 

 The great grain elevator at Milwaukee, Wis., is to be raised sev- 

 eral feet, in the manner the Fremont House, at Chicago, was raised 

 not long ago. The elevator is two hundred and eighty feet long, 

 eighty-six feet wide, and one hundred and thirty feet high, and is 

 estimated to weigh ten thousand tons. Timbers are placed in four 

 hundred recesses in the foundation of the building, which are to 

 sustain it. Underneath these timbers are placed one thousand 

 six hundred large screws, which are to be turned by means of 

 levers, until the building is brought to the required height, when 

 a new foundation will be placed under it. The cost of the work 

 will be about thirty thousand dollars. 



MAGNETIC AND DIAMAGNETIC EXPERIMENTS. 



M. Chantard has reported to the French Academy of Sciences 

 his plan of illustrating the action of an electro-magnet on certain 

 gases. He uses Plateau's mixture of soapsuds and glycerine. To 

 show, for instance, that oxygen gas is magnetic, he forces it through 

 the mixture, thus forming tough soap bubbles filled with oxygen 

 gas. As these pass the poles of the electro-magnet, they are 

 attracted; but when the current is broken, they fall by their supe- 

 rior gravity. By throwing the powerful rays of Hare's lime light 

 on the bubble, the experiment was plainly seen by a lage assembly. 



ESTIiilATION OF METALLIC SILVER. 



According to Clawson, silver is wholly precipitated from a solu- 

 tion of sulphate of silver by plunging into it a plate of cadmium. 

 The silver is deposited in a compact mass, easily washed with 

 water; to remove any traces of cadmium, boil the silver in the 

 acid liquid until no hydrogen escapes; wash it until the water is 

 free from sulphuric acid; then dry and calcine it. The silver is at 

 first a black gray, but soon takes a metallic luster. On weighing, 

 the result is found to be very exact. When dealing with nitrate 

 of silver in solution, evaporate it to dryness in the presence of sul- 

 phuric acid, and then dissolve the sulphate of silver in boiling 

 water, when it will be ready for receiving the metal, cadmium. 



INFLUENCE OF CAPILLARITY ON CHEMICAL ACTION. 



M. Becquerel has communicated to the French Academy of 

 Sciences, his series of experiments on the influence of the capil- 

 laritj^ on chemical decompositions and combinations. He makes, 

 in a tube having two reversed branches, a fissure of infinitely small 



