552 



Mr. G. Ansdell and Prof. J. Dewar. [June 10, 



Such a large quantity of water was condensed in the bulb tube in 

 heating the Dhurmsala meteorite, it being the first one examined, that 

 it was thought it might be principally due to the great absorptive 

 power of these porous bodies, and that therefore the moisture might 

 have been condensed in the pores of the meteorite from the surround- 

 ing air. The Pultusk and Mocs specimens appeared to be especially 

 adapted for ascertaining whether this was the case, as the complete 

 covering of black glaze would probably prevent the moisture from 

 penetrating to the interior of the stones. The fragments of these 

 stones were therefore transferred as quickly as possible to the com- 

 bustion tube after they had been broken up. Notwithstanding these 

 precautions, fully as much water was condensed from them as from the 

 Dhurmsala specimen, which seems to suggest that the water is really 

 combined in some form in the stone and not obtained directly from 

 the surrounding atmosphere, although it must be admitted that the 

 glaze on both the stones was not of a very glossy character, and did 

 not have the appearance of being absolutely impervious to moisture. 



The pumice-stone was examined merely with a view to comparing 

 the gases occluded by a porous body of volcanic origin with those 

 contained in meteorites. The sample taken was a fresh piece of stone, 

 which had not been dried or purified in any way. 



It is evident that it differs considerably from the meteoric stones, 

 the total occluded gas being very small, only about half its volume, 

 the carbonic acid at the same time being much less with a propor- 

 tionate increase in the carbonic oxide. 



The general method of analysis was as follows, and the accuracy of 

 the results was confirmed by varying in some cases the method of 

 separating the gases. The carbonic acid was first removed from the 

 mixture by caustic potash, the carbonic oxide being then absorbed by 

 subchloride of copper, and the remainder of the gases exploded with 

 excess of oxygen. The carbonic acid formed was again removed by 

 caustic potash, and the excess of oxygen by alkaline pyrogallate, the 

 residue being taken as nitrogen. The relative quantities of marsh-gas 

 and hydrogen were calculated from the total diminution after explo- 

 sion, and the amount of carbonic acid formed : — 





Sp. gr. 



Occluded 

 gases in 

 vols, of the 

 meteorite. 



Percentage composition. 



co 2 . 



CO. 



H. 



CH 4 . 



N. 



Dhurmsala. . . . 



3-175 



2-51 



63-15 



1-31 



28-48 



3-9 



1-31 



Pultusk 



3-718 



3 54 



66-12 



5-40 



18-14 



7-65 



2-69 





3-67 



1-94 



64-50 



3-90 



22-94 



4 41 



3-67 



Pumice-stone. . 



2-50 



0-55 



39-50 



18-50 



25 4 





16 60 



