20 Professor Bischof s Reasons against 



remains in sedimentary rocks come in contact with the liquid 

 ignited matters in the focus of a volcano. 



Passing from this matter, I shall turn to the supposition of 

 an oxidation of the earthy and alkaline metals at the expense 

 of water. Professor Daubeny alleges to my objections- con- 

 cerning the disengagements of enormous quantities of hydro- 

 gen in such a case, that this gas could hardly be expected to 

 escape in a free state from a spot which contains so many 

 elements, for which it possesses a strong affinity, and to which 

 it would be presented under the influence of the pressure and 

 temperature so well calculated to promote its combination 

 with them. 



Venturing to offer some remarks against these consequences, 

 I shall first endeavour to calculate what quantities of hydrogen 

 ought to be separated, on the supposition that a certain quan- 

 tity of lava would be generated by oxidation of their metallic 

 principles, at the expense of water. I shall then examine into 

 the possible combinations which hydrogen may be assumed to 

 present in the focus of a volcano. 



As for the calculation, I shall found it on that given by 

 Daubeny, above quoted. 100 parts of lava contain 42 parts of 

 oxygen, and these are contained in 47.6 parts of water. We 

 may consequently suppose that lava, when formed by the oxi- 

 dation of its metallic principles at the expense of water, re- 

 quires about 50 per cent, of it. Lava being 3.2 times heavier 

 than water, 1 volume of the former will require about 1.5 vo- 

 lumes of the latter to be produced. The lava ejected from 

 the Skaptar Jokul would, of course, have required a bulk of 

 water 1.5 times as much as that of Mont Blanc. 



I feel disposed to believe that the explanation, as to how 

 such considerable masses of water may gain admittance to the 

 focus of a volcano, is less difficult than the supposition that 

 there are substances in sufficient quantity for uniting Avith so 

 great an amount of hydrogen as would be separated by the 

 decomposition of that water. 



Professor Daubeny mentions the sulphur and chlorine we 

 know to be generally present in volcanos. As 6.188 parts of 

 hydrogen unite with 93.812 parts of sulphur to produce 100 

 parts of sulphuretted hydrogen, 5.6 parts of hydrogen separated 



