80 Intelligence and Miscellaneous Articles. 



The employment of solar light permits the reference of the ab- 

 sorption-curves to the Fraunhofer lines, and consequently to the 

 wave-lengths of the different points in the spectrum. If the 

 prisms were replaced by networks, we should have a simpler repre- 

 sentation of the relation connecting the coefficients of absorption 

 with the different wave-lengths. When, however, we wish to 

 study, with respect to chromatic absorption, substances endowed 

 with a very feeble absorptive power, or desire to express more pre- 

 cisely the law of extinction for all the radiations, the process just 

 described is scarcely suitable. In this case photometric means 

 must be used, and recourse be had to the law of monochromatic 

 absorption admitted by physicists for interpreting the results. — 

 Comptes Rendus de VAcademie des Sciences, Dec. 3, 1877, tome lxxxv. 

 pp. 1046-1049. 



THE LIQUEFACTION OF OXYGEN. 

 One of the most interesting experiments in physics of our times 

 has just been performed at Greneva, with rare success, in the works 

 of the Physical-Instrument Manufacturing Company. Our fellow 

 citizen, M. liaoul Pictet, has succeeded in obtaining, by means of 

 ingeniously combined apparatus, the liquefaction of oxygen gas. 

 The following are, briefly, the principles by aid of which this impor- 

 tant result has been obtained: — By a double circulation of sulphurous 

 and carbonic acids the latter gas is liquefied at a temperature of 

 65 degrees of cold under a pressure of 4-6 atmospheres. The 

 liquefied carbonic acid is led into a tube of 4 metres length ; two 

 combined-action pumps produce a barometric vacuum over this 

 acid, which solidifies in consequence of the difference of pressure. 

 Into this first tube (containing, as just said, solidified carbonic 

 acid) passes a narrower tube, in which circulates a current of oxy- 

 gen, produced in a generator containing chlorate of potass, and 

 having the form of a large howitzer-shell with walls thick enough 

 to prevent all risk of explosion. The pressure may be carried as 

 far as 800 atmospheres. Yesterday morning, all the apparatus 

 being arranged as just indicated, under a pressure not exceeding 

 300 atmospheres, a liquid jet of oxygen spirted from the end of 

 the tubes at the moment when the compressed and refrigerated gas 

 was passing from this high pressure to the atmospheric. What 

 gives to this fact its great scientific interest is, that it experimen- 

 tally demonstrates the truth of the mechanical theory of heat, by 

 proving that all gases are vapours, capable of passing through the 

 three states — solid, liquid, and gaseous. A fortnight since, M. 

 Cailletet had succeeded in liquefying nitric oxide, under a pressure 

 of 146 atmospheres, and at 11 degrees of cold. After the experi- 

 ment of M. Raoul Pictet there remain only two gases that have as 

 yet escaped the test of liquefaction — hydrogen and nitrogen. The 

 fine experiment above described will, we are informed, be repeated 

 on Monday next, and following days, with some slight changes in 

 the processes and arrangement of apparatus. — Journal de Geneve, 

 December 23, 1877. 



