P OL YTECSmC A SSO CIA TION Pr CEEDINGS. 639 



first the color will be brown, but if retouched two or three times, 

 it will become reddish. If the solution contains one-eighth of 

 common soot and one-eighth of bi-tartrate of potash, it will give a 

 grayish-brown color. A violet color is obtained by substituting 

 alum for the two substances last named. A solution of chloride 

 of ffold erives a lisfht brown color, and nitrate of bismuth white and 

 opaque appeai'ances. These colors are unaffected by the atmos- 

 phere; they will reappear after washing when exposed to sunlight. 



A WTNTEK LANDSCAPE. 



In Germany materials are put up and sold for making an inter- 

 esting chemical experiment. They consist of a solution of nitrate 

 of lead, one part; and water, three parts; also, of sal ammoniac 

 (chloride of ammonium) in fragments of about the size of small 

 beans. The solution, which is a colorless liquid, is poured into a 

 bottle or glass to the depth of, say, two inches, and then pieces of 

 sal ammoniac are dropped in to cover the bottom. A double 

 decomposition takes place, and a white crust is deposited, forming 

 miniature representations of trees, grasses, and rocks covered with 

 snow. Those who intend to repeat the experiment must bear in 

 mind the fact that the nitrate of lead is poisonous. 



A MmiATUKE VOLCANO. 



Prof. Choutard, filling the chair of Natural Philosophy at Nancy, 

 France, has devised the following experiment, showing the power 

 of Euhmkorff's induction coil. A quantity of the flowers of sul- 

 phur is mixed with a small proportion of iron filings, or, better 

 still, with iron reduced by hydrogen, in which case it is in quite 

 an impalpable state; zinc and copper filings may also be added in 

 small quantities. The mixture, made as complete as possible, is 

 placed on a pane of glass or a dry brick, so as to form a heap two 

 or three centimeters high, and much longer than broad. The ends 

 of the wu-es of a Euhmkorff's apparatus are inserted into the heap, 

 so as to be two or three centimeters distant from each other. When 

 ready, a current of electricity is sent through the coil, and instantly 

 a violent explosion takes place. A sort of crater is formed, whence 

 magnificent sheaves of fire are seen to issue, displaying colors like 

 a bouquet of fireworks. It is in reality a volcano, on a very small 

 scale, having its subterranean noises, as it were, and ejecting boil, 

 ing lava. 



KRUPP'S GUN. 



The great cast steel gun exhibited by Krupp, of Essen, at 

 the Paris Exposition, weighs, including the breech, fifty tons. The 



