550 Mr. G-. Ansdell and Prof. J. Dewar. [June 10 ? 



cent, carbonic oxide. He was followed in 1872 by Wohler ("Pogg. 

 Ann.," vol. 146, p. 297) and Berthelot (" Compt. rend.," vol. 74, pp. 

 48, 119), who estimated approximately the gases contained in the 

 Greenland Ovifak iron. These gases consisted of about equal parts 

 of carbonic acid and carbonic oxide ; the celestial origin of this iron is, 

 however, very doubtful. 



In the same year (1872) the American chemist, Mallet (" Proc. 

 Roy. Soc," vol. 20, p. 365), made a very complete determination of the 

 gases occluded by the Augusta Co., Virginia, meteoric iron, which, 

 however, differed very considerably from Graham's results. He 

 obtained an amount of gas equal to 3'17 times the volume of the iron, 

 made up of 35*83 per cent, of hydrogen, 38*33 per cent, carbonic oxide, 

 9*75 per cent, of carbonic acid, and 16'09 per cent, of nitrogen. 



Wright and Lawrence Smith followed Mallet, and our present know- 

 ledge of this interesting subject is principally due to these American 

 chemists. They have taken advantage of the numerous meteoric 

 masses which have fallen from time to time throughout America,, 

 and which can easily be obtained in sufficient quantity for complete 

 and accurate observations on their gaseous constituents. 



Wright contributed several papers to the " American Journal " in 

 1875 and 1876, and, according to his analyses, the total volume of gas- 

 occluded and the composition of the same differs considerably in the 

 two principal classes of meteorites. He found the total volume of 

 gas extracted was much greater in the case of the stony meteorites 

 than in the iron ones, the principal characteristics of these gases 

 being, that in the former the carbonic acid greatly predominated, 

 accompanied by a comparatively small amount of carbonic oxide and 

 hydrogen, whereas in the latter the carbonic acid never exceeded 

 20 per cent., the carbonic oxide being, as a rule, considerably more 

 than this, and the hydrogen sometimes reaching as high as 80 per cent. 



It is impossible, however, to arrive at anything more than general 

 conclusions as to the total amount of gas given off by any special 

 meteorite, or its composition, for, as shown by Wright and confirmed 

 by ourselves, both the total quantity and composition of the gases 

 vary very considerably according to the temperature at which they 

 are drawn off. 



Wright found a notable quantity of marsh-gas in all the stony 

 meteorites which he examined, though not a trace in any of the iron 

 ones; this seemed to be a distinctive difference between the two 

 classes of meteorites, but subsequently Dr. Flight, of the British 

 Museum ("Phil. Trans.," vol. 173 (1882), p. 885), found marsh-gas 

 in a specimen of the Cranbourne siderite, so that it is evident certain 

 of the iron meteorites also contain this gas. 



Lawrence Smith ("Amer. Journ.," 1876) confined himself princi- 

 pally to an examination of the graphite nodules which are frequently 



