HARDWICKE'S SCIENCE-GOSSIP. 



us, his audience, the snow-like solid at his next lecture, 

 and how he fulfilled his promise by appearing in 

 miserable plight with bandaged head and face, due 

 to the explosion of a Thilorier cylinder he had used. 

 He narrated the accident, attributing it to insufficient 

 thickness of the cylinder, but he had now another 

 stouter cylinder similarly charged in front of the 

 lecture table which he hoped would resist the pressure. 

 The front benches of the theatre were cleared forth- 

 with, in spite of his hope. 



It has remained merely a scientific curiosity nearly 

 ever since, but now promises to become very useful. 

 Messrs. Rayclt and Kunheim produce it in Germany 

 commercially, and hope to profit by its applica- 

 tions to the charging of beer in the cask, to 

 the manufacture of aerated waters of all kinds, by 

 simply introducing the necessary quantity of the snow 

 which expands, and at once produces the required 

 aeration. It is a most efficient fire extinguisher. 

 A suitable vessel containing it and flung into the fire 

 explodes when heated, and diffuses all around an 

 atmosphere of carbonic acid gas in which no com- 

 bustion can occur. For various purposes, where great 

 compression is demanded, it may be used with very 

 simple appliances. The Krupps find that a heat of 

 360 applied to it gives the enormous pressure of 1200 

 atmospheres. It may be used instead of compressed 

 air for the raising of sunken ships. 



Condensation of Gases. — Until nine years ago 

 the old descriptive distinction between permanent 

 gases and condensible vapours still remained, but on 

 the 24th December, 1877 its lingering existence was 

 finally extinguished by the announcement to the 

 French Academy of Science that oxygen gas had 

 been liquefied by two independent experimenters, M. 

 Cailletet a French ironmaster, and Raoul Pictet a 

 Swiss manufacturer of icemachines. The other gases, 

 which up to this date had resisted all attempts to 

 condense them, were speedily overcome, and now we 

 may say every element may be a solid, a liquid, or a 

 gas, according to the temperature and pressure to 

 which it is subjected. The chief agent in obtaining 

 these successes is ethylene, a liquid that boils at a 

 temperature of — 238 F., i.e. 270 degrees below 

 freezing. In the act of boiling it absorbs much heat, 

 robs all its surroundings and cools them down as 

 water cools the surface of our bodies by its eva- 

 poration. When thus cooled down to 184 below 

 freezing, chlorine forms orange coloured crystals; 

 at 23 2 below freezing, ether solidifies ; at 234 

 absolute alcohol is a solid ; at 331 ° liquid oxygen 

 boils ; at 344 air is liquid, and it boils in vacuo at 

 369 degrees below freezing. The lowest temperature 

 yet obtained is —373 F., or 395 below freezing. The 

 absolute zero is supposed to be — 459 F. I say " is 

 supposed," not that I suppose, my own supposition 

 being that we know nothing about absolute tempera- 

 ture, or absolute anything else. 



Sea Air. — Professor F. S. Dennis, of New York, 

 states that in the course of a trip across the Atlantic 

 he made some experiments on the air about 1000 

 miles distant from land. He exposed capsules of 

 sterilized gelatine for 15 minutes. No. 1 in the State 

 Room upon the main deck of the steamer ; No. 2 

 and 3 in a cabin on the promenade deck where the 

 circulation was free ; and No. 4 over the bow of the 

 ship. Within 18 hours 500 points of infection had 

 developed in No. 1 ; only five and six in Nos. 2 

 and 3 after ten'days ; and none at all in No. 4. By 

 "points of infection" he means of course, bacteria ; 

 bacilli, or some kind of microbia, that may or may not 

 be poisonous. The absence of such possibly mis- 

 chievous forms of life over the sea, and as Tyndall 

 has shown over the higher ground of the Alps, is 

 very interesting, but we should not overrate its 

 importance. The simple fact that an hour or two 

 after most vigorous tooth brushing anybody may 

 scrape myriads of microbia from his teeth, and 

 tongue and palate — and most of these "comma- 

 shaped "—should teach us not to be panic-stricken by 

 the rapid generation of large numbers in experi- 

 mental gelatine. A single whiff of the breath of the 

 experimenter himself is sufficient for the establish- 

 ment of a flourishing colony. If Professor Dennis 

 had stood for 15 minutes at the bow of the ship with 

 one capsule 2 or 3 feet forward of his face, and 

 another behind his head he would probably have 

 found a great difference between them, due to his- 

 own exhalations. 



Successful Oyster Culture. — The report of 

 Mr. Saville Kent, Superintendent and Inspector of 

 Fisheries to the Tasmanian Government, is very 

 satisfactory. The success of the oyster beds is com- 

 plete, and this success appears to be due to the fact, 

 that the Tasmanian Government has put the right 

 man in the right place. Everybody who knew Mr. 

 Kent when in England knows that he is a devoted 

 student of the subject in which he is now officially 

 engaged. His report shows that oysters may be 

 sown and reaped as reliably as potatoes, i.e. with 

 only rare occasional failure. But to obtain such- 

 success the sower must understand his business, must 

 select suitable places for the beds, where there is 

 moving water containing sufficient food, and where 

 proper arrangements are made for catching' the spat 

 in such wise that it shall not be smothered with 

 sedimentary mud. The spat collectors used by Mr. 

 Kent are cheap wooden frames that may be rocked 

 or lifted to shake away the sediment. They are 

 fully described in the report. 



The present oyster famine in the British Isles is a 

 national disaster and disgrace. The ancient Romans- 

 sent to Britain for their oysters and now we cannot 

 supply ourselves, but are dependent on Portugal, 

 Holland, and the United States. In a few years, 

 hence we shall probably import tinned oysters from 



