208 Prof. C. Olszewski on the 



So far as the accuracy of photometric measurements under 

 such difficult conditions could be relied upon, we found a 

 proportion of light varying between 81 and 89 per cent., 

 transmitted by a layer of oxygen 1 millim. in thickness in 

 the most intense part of the yellow-greenish band (A = 577 to 

 X = 570). The corresponding average number for the red 

 band (A, = 630 to X=638) was 88 per cent. 



In the same pamphlet we described a method of deter- 

 mining the coefficient of refraction of liquid oxygen and gave 

 results for sodium light. The most suitable method for the 

 purpose proved to be that of total reflexion. The liquid is con- 

 tained in a thin iron parallelepipedon A (see fig. 5), pro- 

 vided with plane glass windows, and protected by several 

 varnished pasteboard boxes of similar form containing some 

 phosphoric anhydride. A double glass plate, composed of 

 two carefully selected plane bits of glass, separated at the 

 corners by small pieces of mica (thickness about 0*006 millim.) 

 and cemented at their obliquely-ground borders by means of 

 fish-glue, is immersed in the oxygen. The double plate is 

 rigidly collected with the axis of a divided circle. A similar 

 arrangement has been employed by Ketteler in some of his 

 investigations on the refraction and dispersion of water 

 (Wiedemann's Annalen, vol. xxxiii.). It is therefore un- 

 necessary to enter into particulars as regards the mode of 

 observation and calculation of results. A first series of 

 observations gave the value 1*2235 of the coefficient for 

 sodium light, in very close agreement with a result found 

 by Messrs. Liveing and Dewar by means of the prism method. 

 Later determinations of the same constant by myself and 

 Prof. Witkowski, made with the view of ascertaining the 

 dispersion of liquid oxygen (Bulletin International, July 

 1894), yielded a rather smaller result (1*2226) as a mean of 

 five distinct measurements. At the same time we found 

 n = P2213 for X= 670*5, and 1-2236 for the wave-length 

 535 /jl/jl. Anomalous dispersion, specially sought for, could 

 not be detected. 



Besides these researches I have made (partly by myself, 

 partly in collaboration with Prof. Witkowski) certain hitherto 

 unpublished experiments concerning the intensity of chemical 

 energy at low temperatures ; I mention them here to com- 

 plete the list of my investigations. They refer chiefly to two 

 substances, viz. liquid ethylene and oxygen, under the in- 

 fluence of agents which combine with these substances at the 

 usual or at a higher temperature, Ethylene, boiling under 

 atmospheric pressure ( — 102°*5 C.) was submitted to the 



