CHEMICAL SCIENCE. 181 



the middle. One of those in silver, and one in bronze, were placed 

 in the stereoscope, the eagle being fixed in the middle. After some 

 time the stereoscopic combined medal was seen in the form of a 

 hollow escutcheon, and of the colour of an alloy of the two metals. 

 Evidently the reason of this lies in the nonius-like shifting of the 

 individual lines of the impression. This result, which Prof. Dove 

 has described (Optische Studien, p. 29), he has also obtained with 

 large gold and silver medals which were kindly entrusted to him 

 from the lioyal Mint in Berlin. It was thought probable that 

 medals obtained by casting would show the same thing, and this 

 was found to be the case with tin, bismuth, and lead. The casts 

 were very beautifully executed for him for this purpose by Pro- 

 fessor Kiss. Hiero's crown led to the application of specific gravity 

 to detect an adulteration ; the stereoscope is a new means. — Pog- 

 gendorff's Annalen ; Philos. Mag., No. 133. 



LEAF-ALUMINIUM. 



M. Degousse, a goldbeater in Paris, has succeeded in preparing 

 Aluminium in fine plates like gold or silver. The operation of beat- 

 ing is effected in the usual manner, but it is necessary that the 

 reheating be more frequent ; the fire of a chauffer is most suitable. 

 Aluminium-leaf may replace sdver in many cases ; its white, though 

 less brilliant, is more durable. 



Wohler has the following remarks on Degousse's leaf-aluminium. 

 It is readily combustible ; if held in the edge of a spirit-lamp flame, 

 it takes fire and burns with great brilliancy. It is very thin ; a 

 cubic inch only weighs a milligramme. If a leaf of it be pressed 

 together, placed in a bulb and heated by means of a spirit-lamp in a 

 current of oxygen, it burns instantaneously with a dazzling lightning- 

 like appearance. The resultant alumina is fused, and as hard as 

 corundum. Aluminium wire also burns in oxygen like iron ; but 

 the combustion does not proceed far, for the next parts melt away 

 before they have reached the temperature of combustion. Alu- 

 minium in the compact form does not decompose water, but the leaf, 

 when placed in boiling water, decomposes a sufficient quantity to 

 enable the hydrogen to be collected. The metal assumes at first a 

 faint bronze surface colour. After several hours' boiling, the 

 laminae become partially translucent, that is, converted into alumina. 

 If the residue be treated with hydrochloric acid, the unoxidized 

 metal is dissolved, while the alumina remains undissolved. 



KESEARCHES ON OZONE. 



M. Le Poux states that if a platinum wire, not too large, be made 

 incandescent by an electric current in such a manner that the as- 

 cending flow of hot air which has surrounded the wire comes into 

 direct contact with the nostrils, an odour of Ozone is perceived. The 

 experiment maybe made in the following manner: — A very fine 

 platinum wire ( T Vth to -^th of a millimetre) 20 centimetres long is 

 taken ; it is formed in any shape, and supported in an almost hori- 



