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Profs. G. D. Liveing and J. Dewar. [June 6, 



concerns the three principal bands, which were all that conld be 

 seen in the light transmitted by the liquid in a thickness of 12 mm. 



It will be observed that taking the density of oxygen at — 181*4° 

 to be 1*124, as given by Olszewski, 12 mm. of the liquid would be 

 equivalent to 9*37 metres of the gas at atmospheric pressure — hardly 

 more than half the thickness required to make A visible. The expe- 

 riments, therefore, point to the conclusion that gaseous and liquid 

 oxygen have the same absorption -spectrum. This is a very note- 

 worthy conclusion. For, considering that no compound of oxygen, 

 so far as is known, gives the absorptions of oxygen, the persistency 

 of the absorptions of oxygen through the stages of condensation to 

 the state of complete liquidity implies a persistency of molecular 

 constitution which we should hardly have expected. 



In order to compare the absorption of ozone with that of oxygen 

 we employed a tube 12 feet long, made of tinplate fitted with glass 

 ends and coated with paraffin on the inside. We could not use the 

 18 m. steel tube on account of the action of the ozone on the metal 

 which rapidly reduced the proportion of ozone, and also because we 

 could not conveniently cool it. Ozonised oxygen was passed into the 

 tin tube for some time, while the ozoniser and the tube itself were 

 cooled with ice and salt. The lime-light, viewed through the tube, 

 looked very blue, and also the spot of light thrown from the tube on 

 to a sheet of white paper was equally blue, indicating a considerable 

 absorption of the less refrangible part of the spectrum. The absorp- 

 tion, so far as the visible rays are concerned, appeared to be of a 

 general character, for the ^spectroscope revealed only four extremely 

 faint absorption-bands. The centres of these bands were at about 

 the wave-numbers 1662, 1752, 1880, and 1990, and their positions 

 with reference to the bands of oxygen are indicated in the diagram. 

 They were so faint as to be seen only with difficulty. When the 

 hot carbon of an arc lamp was substituted for the lime-light they 

 were rather more distinct, but the positions of the edges were un- 

 definable. The light of a gas-lamp was insufficient to show them, 

 and they were no better seen with a single-prism spectroscope of 

 low dispersive power than with the spectroscope we employed for 

 observing the oxygen. Only one of these bands, it will be seen from 

 the diagram, is nearly coincident with an oxygen-band, namely, that 

 near E, the faintest of the oxygen-bands. That at wave-number 

 1752 overlaps the strongest oxygen-band, but not at its strongest 

 part, and has none of the peculiar character of its shading, abruptly 

 increasing on the less refrangible side and slowly decreasing on the 

 other side. Photographs of the spectrum (taken through a tube 

 with quartz ends) showed that the ozone absorbed all the rays above 

 the wave-number 3086 — a point between Q and R — while partial 

 absorption extended below Q. We may say, therefore, that we can 



