CHEMICAL SCIENCE. 181 



" About a half an hour after, I happened to direct my attention to 

 this dish, and found, to niy great surprise, that the surface in the dish 

 was coated with a thin, brilliant, uniform layer of metallic silver. I 

 directly repeated the experiment, and met with the same result again 

 and again. I next proceeded to evaporate the liquid to dryness by 

 placing the dish on the surface of warm sand. As soon as it was 

 completely dry, the coating was found to be so fast on the porcelain 

 that it required the point of a sharp penknife to scrape it off. 



" From these experiments I would venture to conclude that porce- 

 lain, and any other stony and smooth surface, might be plated with 

 silver, and if so, it might be useful in many of the arts. I would add, 

 in conclusion, that I also succeeded in producing a metallic brilliant 

 coating from a saturated solution of sulphate of copper by the same 

 solution of tannin." 



ARTIFICIAL GEMS. 



A beautiful red-colored stone, called " Rubasse," has lately been 

 popular in Paris, and brought high prices to the jewellers. Schaff- 

 gotsch examined a specimen, and found that, when placed in ammo- 

 nia, it soon lost its beautiful color, and became a simple piece of rock 

 crystal. It was, indeed, a specimen of quartz, the minute fissures in 

 which had apparently been filled with a solution of carmine. 



Artificial Diamonds. We find a report in French journals, that 

 M. Gannal has succeeded in obtaining crystals having all the proper- 

 ties of the diamond, through the mutual reaction of phosphorus, water, 

 and bisulphide of carbon upon each other, for the space of fifteen 

 weeks. The crystals were found to be so hard that no file would act 

 upon them ; they cut glass like ordinary diamonds, and scratched the 

 hardest steel ; in brilliancy and transparency they were in no way 

 inferior to the best jewels, and some few possessed a lustre surpassing 

 that of most real stones. 



Last, not least, the substance so produced was crystallized in dode- 

 cahedra, the crystalline form characteristic of the diamond. 



EFFECT OF GREAT PRESSURE ON THE SIX NON-CONDEJSTSI- 



BLE GASES. 



At the last meeting of the British Association (1861), Dr. Andrews 

 gave an account of some researches made by him on the changes of 

 physical state which occur when the non-condensible gases are ex- 

 posed to the combined action of great pressures and low temperature. 

 The gases when compressed were always obtained in the capillary 

 end of thick glass tubes, so that any change they might undergo 

 could be observed. In his earlier experiments the author employed 

 the elastic force of the gases evolved in the electrolysis of water as 

 the compressing agent, and in this way he actually succeeded in 

 reducing oxygen gas to l-300th of its volume at the ordinary pres- 

 sure of the atmosphere. He afterwards succeeded in effecting the 

 same object by mechanical means, and exhibited to the Section an 

 apparatus by means of which he had been able to apply pressures 

 which were only limited by the capability of the capillary glass tubes 

 to resist them ; and while thus compressed the gases were exposed to 



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