142 Progress in Science. [January, 



elements, by which means the horseshoe might be magnetised either posi- 

 tively or negatively at pleasure. The variations were indicated by a small 

 horizontal needle situated in the plane of the poles. There was, further, a 

 series of iron plates, which could be separately applied to each of the laminae, 

 Before attaching any of the latter, the electric current was driven through the 

 apparatus for a few minutes and then interrupted, whereby the magnet 

 acquired its first degree of saturation, marked by a certain deviation of the 

 needle. One of the iron plates (usually called " contacts ") was then put on, 

 and it supported a weight of 140 kilogrammes. A second trial was now made ; 

 and the current having been passed through again for a few seconds, it. was 

 found that the horseshoe would support 300 kilogrammes, instead of 140. 

 The number of contacts being now increased to five, which together in the 

 natural state supported 120 kilogrammes, it was found after the passage of 

 the current that they could support the enormous weight of 680 kilogrammes, 

 which they did for the space of a week. No sooner, however, were the con- 

 tacts taken off than the horseshoe returned to its usual permanent strength of 

 140 kilogrammes. This tends to show that magnetism may be condensed like 

 electricity for a short period. 



Zollner has ascribed the electric currents of the earth to the motion of in- 

 candescent molten masses beneath the crust, which generate currents in the 

 direction of their motion. He has also stated that all current movements of 

 fluids, especially when in contact with solid bodies, are to some extent 

 accompanied with currents of electricity, which have the same direction as 

 the fluids themselves. To prove this he inserted the ends of the copper wires 

 of a very delicate galvanometer just within the wall of a caoutchouc tube, 

 through which a stream of water was passing ; this caused a deflection of 

 several degrees on the galvanometer scale, thereby indicating the existence 

 of an electric current, whose direction was that of the water. The greater the 

 distance between the ends of the wires, which may be replaced by metallic 

 plates, the stronger the deflection of the needle. Beetz, while recently re- 

 peating Zollner's experiment, obtained similar results, but found that the 

 currents have a much simpler origin. The needle is deflected so long as the 

 reservoir in which the water falls is not isolated. The metal, the stream of 

 water, and the reservoir, form a voltaic element, whose current it is that 

 deflects the needle. By filling the reservoir, and dipping the free end of the 

 tube, also filled into it, the current is observed though the water be shut off, 

 nor does any change take place when the tap is opened. By simply inverting 

 the position of the tube, the direction of the current is reversed; this is ob- 

 served to be the case with or without a flow of water. If the reservoir is 

 isolated, no current is formed, whether the water be allowed to flow or not. 

 When the tap and reservoir are of zinc, no current is produced with or without 

 a flow of water, and with or without isolation of the reservoir. Therefore, 

 according to these observations, no electricity is generated by a stream of 

 water. 



TECHNOLOGY. 

 Professor Chevreul has made a series of experiments on the stability of 

 dyes imparted to silks, damasks, and fabrics used in furnishing, The blue 

 colours produced by indigo are stable ; Prussian blue resists moderately the 

 action of air and light, but not of soap ; scarlets and carmines produced by 

 cochineal and lac-dye are fast ; the most stable yellows on silk are produced 

 by weld. 



M. Dubrunfaut, during the siege of Paris, devised an artificial milk, made 

 by dissolving one ounce and a half of sugar in a quart of water, -adding an 

 ounce of dry albumen (from white of eggs), and 15 to 30 grains of soda crystals, 

 and then making an emulsion with it by means of from one ounce and a 

 half to two ounces of olive oil. As the war progressed gelatine was substituted 

 for albumen, and slaughterhouse fats, purified by melting at 150 , for the 

 olive oil. One firm made by the latter process 132,000 gallons of milk daily 

 for Paris consumption. 



M. E. Daniel states that painting in oil may be executed upon tin-foil spread 



