4:26 R W. Hilgard— Geology of the Delta., 



mouths ; and unless it were conclusively proven that the mat- 

 ters ^'ected hy the mvd-springs were such as could not originate 

 in the present delta formation, the artesian hypothesis must lose 

 all show of probability. An accurate investigation of the mat- 

 ters in question, solid, liquid, and gaseous, was therefore 

 indicated. A few specimens for this purpose were collected for 

 me by Mr. Marindin, in 1867 ; but the perusal of his report 

 accompanying them convinced me that a personal examination 

 in loco could alone insure a perfect certainty as to their signifi- 

 cance, and accordingly, in the autumn of the same year, 1 

 re-collected specimens from the same, as well as from other 

 localities. Very unfortunately, the arrangements for gas analy- 

 sis at my command were so imperfect that, while waiting for 

 their improvement, the gas specimens were so vitiated hy diflfu- 

 sion through corks and wax as to render them useless; and I 

 have been unable to replace them as yet, but hope to do so in 

 the near future. 



Mudlump Gases.— ThQ examination of the water and mud 

 seemed, however, most likely to conduce to a solution ot the 

 problem, at any rate ; for after all, the only information which 

 could be furnished by gas analysis would be to indicate, by the 

 greater or less amount of carbonic acid present, whether the gas 

 originated from matter comparatively fresh and in its first stage 

 of decomposition, or had its source in materials far advanced 

 toward the stage of lignite or coals. The only perfectly rehabje 

 determination made was that of the carbonic acid contained in 

 the gas collected from the most easterly active cone on Marin- 

 din'sLump, Passeal'Outre, the rest of the determinations bang 

 somewhat vitiated, though doubtless very nearly correct* Ine 

 result was as follows : 



Gas from East Crater, Marindin' s Lump, Passe d F Outre. 



Carbonic acid, 9*41 



Marsh gas, -- 86-20 



Nitrogen, 4"39 



100^ 



Oxygen was not present. . ■,, 



The percentage of carbonic acid in this gas is very unusually 

 large ; its composition is nearest to that of the gas from com- 

 mon swamps, where vegetable matter is in its first stages ot de- 

 cay. The proportion between marsh gas and nitrogen is near 

 the same as in the gas from the gas wells at New Orleans (see 

 p. 245) ; but there is three times as much carbonic acid presen 



♦After the explosion in the eudiometer, some nitrate of mercury was obsei^ed on 

 its walls, in consequence of inadequate dilution of the gas. But tiie ^^'^J^^^ 



