HARDWICKE'S SCIENCE-GOSSIP. 



59 



Fluorine. — The old alchemists devoted their lives 

 to searching for the three arcana, the philosopher's 

 stone, the aurum potabile (drinkable gold), that would 

 endue the body with the imperishable properties of 

 the noble metal, and thus give immortality to the 

 drinker, and the universal solvent which was to do 

 much towards rendering the gold thus drinkable. A 

 logical sceptic suggested a difficulty incident to the 

 third of these, viz. that if it dissolved everything 

 nothing could contain it, as any vessel of whatever 

 material would yield to its solvent powers. Modern 

 chemistry has actually supplied us with such an 

 untenable material in the element fluorine. It has 

 been produced for a moment, but combines imme- 

 diately with whatever it touches, and thus instead of 

 free fluorine, a fluoride of something is obtained. M. 

 Debray, however, has recently reported to the French 

 Academy of Sciences that M. Moissan has at last 

 succeeded in isolating this refractory element. He 

 obtains it in the form of a gas which decomposes cold 

 water with disengagement of ozone ; phosphorus 

 burns in it, silicon does the same. It may possibly 

 be a compound with hydrogen, but M. Moissan 

 discusses this hypothesis and concludes that it is 

 really free fluorine. We may hear something more 

 about collecting and retaining it hereafter. 



London Fogs in Paris. — The bucks of Paris 

 imitate Englishmen quite as much as English ladies 

 of fashion imitate French women. Lately the atmo- 

 sphere of Paris has adopted London fashions, has 

 infringed our patent right in the monopoly of pea 

 soup fogs. The fact is instructive, as it evidently 

 proceeds from the continually increasing use of coal 

 fuel in Paris. The two cities are similarly situated, 

 each in the trough of a long river valley where mists 

 are liable to rest — such mists, if no city were there, 

 would be the ordinary white mists of the country, 

 ■consisting of minute spheres of water (vesicles have 

 been disproved) surrounding still more minute parti- 

 cles of solid matter. But coal, when burnt in an 

 ordinary fireplace where the combustion is imperfect, 

 gives off tarry vapours and these are condensed upon 

 the water particles as a tarry varnish, which not only 

 colours them but gives them their acrid, irritating 

 character. The coal further increases the liability 

 to fog by sending into the atmosphere particles of 

 sulphur sublimed from the pyrites in the coal. As 

 Aitken has shown, these are most potent fog pro- 

 ducers. By subliming an unweighably small quantity 

 •of sulphur into the midst of our atmosphere, saturated 

 with water vapour but still clear, he produced an 

 artificial fog so dense that it was impossible to see 

 through a thickness of six or seven yards. Let us hope 

 that Paris and London will co-operate to abate their 

 fogs and abolish the smoke nuisance altogether. 



Oyster Culture.— I have received the follow- 

 ing : — "My attention has been called to a note of 



yours in last Science-Gossip on Successful Oyster 

 Culture. The portion alluding to the fact of Mr. 

 Kent succeeding with oysters at the Antipodes, and 

 his qualification for the task, cannot be taken ex- 

 ception to, but as one who has spent much money, 

 care, and attention on the matter in question, and 

 who is still experimenting on a practical scale, I 

 must demur to the latter portion. The temperature 

 in Tasmania is no doubt higher and probably more 

 equable than ours, but for many years neither our 

 native oysters here, imported Americans, small or 

 large, nor imported French, have shown increase. I 

 am thoroughly acquainted with all known systems of 

 oyster culture, and have given the subject my personal 

 and unremitting attention for seven or eight years 

 without success, entirely, so far as I can discover, 

 through rapid and extensive variations of tempera- 

 ture. This would not take effect at greater depths, 

 but at these depths the system advocated is impos- 

 sible. You say ignorance stands in the way — then 

 why cannot some one enlighten us ; we have in 

 vain offered prizes (and won them). Oysters keep 

 decreasing ! We want a cycle of years with less 

 rainfall and more summer heat ere we can hope for 

 anything here, for although our oysters occasionally 

 reach the condition of black spat, only a very small 

 proportion of these manage to exist. As the pioneer 

 of ' Oyster Culture ' in Scotland, I should be glad to 

 hear of any one who could ensure success in this 

 country. 



" W. Anderson Smith." 



The subject is of such practical importance and 

 scientific interest that it cannot be too vigorously 

 agitated, and therefore Mr. Anderson Smith's letter 

 is very welcome, as it presents the opposite side to 

 that which I have seen and described in my Gossip 

 of last month. 



In spite of great respect for Mr. Smith's experience, 

 I am still of opinion that ignorance does stand in the 

 way. I am not using the word ignorance in an 

 offensive sense, by any means, but as I should use it 

 in saying that we are in ignorance concerning the 

 laws of variation of British weather. 



As regards extensive variations of temperature it 

 should be noted that John Chinaman had succeeded 

 in his climate, which is one of the riiost exaggerated 

 in the world as regards such variations, whether we 

 consider the difference between summer and winter 

 or night or day. The climate of Scotland is remark- 

 ably agreeable compared with this, or even with those 

 parts of the American coasts which supply us with 

 "blue-points." (I may add, by the way, that on 

 Saturday last I saw large quantities of excellent blue- 

 point oysters offered for sale on costermongers' barrows 

 at sixpence per dozen, pepper and vinegar and the 

 labour of opening included.) 



In the "Gentleman's Magazine "of last April, I 

 described the Chinese method of collecting the spat 



