NOTES on the CONDITION of the ATAIOSI'M i-;j; !•: 



DURING the RECENT CONTACT of the EARTH 



with the TAIL of HAL LEY'S COMET. 



By H. G. A. Harding, a.s.t.c, Sydney Technical College. 



(Communicated by \V. J. Clunies Ross, b.sc.) 



[Read before the Royal Society of N. S. Wales, August 3, 1910.] 



Owing to the possibility of our atmosphere being affected 

 by the recent passage of the earth through the " tail " of 

 Halley's Comet, it was resolved to conduct a series of 

 experiments, to ascertain any appreciable variations in its 

 composition, by analysing samples of air collected before* 

 during, and after the time of contact. The samples were 

 taken daily from suitable positions in the Hornsby district, 

 in calibrated Erlenmeyer ilasks, from about a week previous 

 to the date of contact (May 19th) till a week following 

 that event. 



The apparatus used in the analyses, was similar to that 

 used by Hesse and Herapel, and experiments were also 

 made with the hitter's gas burette, using mercury instead 

 of water as the confining liquid in measuring the gases. 



The percentages of oxygen, carbon dioxide and water 

 vapour were very accurately estimated, every precaution 

 being taken to guard against possible errors in the deter- 

 minations. The oxygen was absorbed by alkaline pyrogal- 

 late, water vapour by aspirating a known volume of the 

 sample through fused calcium chloride (saturated with 

 carbon dioxide) and the carbon dioxide by agitation with 

 standard barium hydrate (25 cc), and the excess titrated 

 with standard oxalic solution. Experiments were also 

 made in absorbing nitrogen by a mixture of lime, metallic 

 sodium and magnesium. 



It was found however, that the composition of the 

 atmosphere remained constant throughout, the several 

 constituents not varying appreciably from normal limits. 



Samples were also submitted to spectroscopic analysis 

 in partially exhausted tubes, specially prepared by the 

 witer, and here again the results indicated nothing abnor- 

 mal in the composition of the atmosphere. 



