300 Intelligence and Miscellaneous Articles. 



■when the coloration has become very intense, the plates continue to 

 disengage gas for a long time after the passage of the current has 

 ceased. 



To resume, the author thinks that the decomposition of water is 

 not a simple phaenomenon, — that electricity first of all produces the 

 pure and simple separation of the elements of water, and afterwards 

 physical or chemical actions, which, although difficult to observe, 

 certainly exist. These are weak in ordinary cases, but are no longer 

 to be neglected where electrodes of large dimensions are employed, 

 and it is to these actions that the anomalies observed in the decom- 

 position must be attributed. — Comptes Rendus, February 27, 1854, 

 p. 390. 



LITHOLOGIC STUDIES. BY C. SAINTE-CLAIRE DEVILLE. 



What are the elements that should guide us in the natural classifi- 

 cation of igneous rocks ? Such is the problem which I have set before 

 me in this first memoir. The very nature of the question, as it was 

 put forward by M. Cordier in the important memoir which he pub- 

 lished in 1815, led me necessarily to re-examine minerals from a 

 particular point of view, that of the part which they take in the for- 

 mation of rocks. In this study I must particularly dwell upon an 

 important notion, first introduced into science by M. Elie de Beau- 

 mont*, the distinction which that geologist has established between 

 matters formed by igneous fusion, or eruptive matters in the manner 

 of lava, and matters volatilized or carried up in the molecular state, 

 eruptive matters in the manner of sulphur, sal ammoniac, &c. The 

 natural divisions which may thus be established in minerals are 

 based, as I show, at once on the characteristic properties of the 

 minerals of each group, on their stratification, and on the labora- 

 tory experiments by which they have been reproduced. 



In the latter part of my memoir I endeavour to indicate what 

 advantage may be derived from the characteristic properties of mine- 

 rals, in establishing the natural relations between rocks which are 

 only aggregates of these various minerals. 



The conditions of stratification which every good classification 

 should indicate, lead me to inquire what ought to be understood by 

 the words — the age of an igneous rock. I close this question, by 

 which lithology enters into relation with stratigraphy, by showing 

 that in each family of rocks the age is in immediate relation with 

 the nature and abundance of the minerals formed in the manner of 

 sulphur ; so that we may say, that this kind of minerals plays in some 

 sort, in the igneous rocks, the part of characteristic fossils . 



The certainty or the probability of these conclusions resting entirely 

 upon the facts brought together in my memoir, some of which are 

 known, whilst others appear to me to be new, it will be readily 

 understood, that, both from its nature and extent, the work which I 

 lay before the Academy is scarcely susceptible of an analysis. I 

 shall therefore confine myself, in concluding this note, to calling 

 attention to some of the prominent points of my work, and which I 



* Des Emanations Volcaniques et Mt'tallifercs, Bull. Soc. Geol. Fr. 

 2nd ser. vol. iv. 



