PETROLOGY. 207 



S. Wales, prolonged S.E. into France, arc bituminous, while those S.W. 

 are anthracitic ; and not only this, but the coals are more altered towards 

 the S.W. in the direction of the lateral extension of the granite of 

 Cornwall. The granites of Dartmoor (which has certainly altered the 

 Culm Measures) and Lundy Island, and perhaps some of those of the 

 N.E. of France, are possibly only partial exposures of a subterranean 

 axis, extending along the line referred to, and which, penetrating at 

 intervals near the Coal Measures, may have developed sufficient heat to 

 drive off some of the gaseous matter. In this way the anthracite and 

 steam coal of Leinster and Lcitrim might have been formed. E. T. H. 



Hardman, E. T. Analyses of Coals and Ironstones from the Dun- 

 gannon Coal-Field, Co. Tyrone. Froc. 11. Irish Acad. ser. 2, vol. 

 ii. no. G, pp. 529-538. 

 8 analyses of coals and 5 of ironstones. The coals are of good 

 quality, highly bituminous, and well suited for gas-making. There 

 are 2 seams of cannel, one equal to the best Lesmahagow coal. The 

 heating power of all is very high. The ironstones are of average com- 

 position, but as yet of no importance. A well-marked point is the 

 complete agreement between the specific gravities and the proportion of 

 ash, a matter that has been disputed ; but this relation holds, not only 

 in respect of these coals, but of most others ; and an approximate idea 

 of the amount of ash of a coal may be had from its specific gravity. 



E.T. H. 



Haughton, Rev. Prof. Samuel, and Prof. Edward Hull. Report 

 on the Chemical, Mineralogical, and Microscopic Characters of 

 the Lavas of Vesuvius from 1G31 to 1868. Trans. B. Irish Acad, 

 vol. xxvi. pt. iii. Science, pp. 49-1G4, plate. 

 Part I. On the Chemical and Mineralogical Composition of the Lavas 

 of Vesuvius. By Rev. S. Haughton. The collection made by Prof. 

 Guiscardi consists of 20 specimens, of which the chemical analyses arc 

 given. From these, and microscopic determination of the minerals, 

 the percentage of the latter constituent is obtained from a series of in- 

 determinate equations, and by the aid of the principle that, " Of the 

 numerous possible solutions, that one wiU occur in Nature which in- 

 volves the largest amount of Definite Minerals and the least amount of 

 Indefinite Paste.' An Appendix, by William Early, gives the methods 

 adopted in the chemical analysis. 



Part II. On the Microscopical Characters of the Lavas. Py Prof. 

 Hull. The lavas are rich in leucite and allied minerals. The speci- 

 mens exhibit a remarkable uniformity of structure ; and the essential 

 and distinctive minerals are leucite and augite ; hence they are leucite- 

 basalt. In certain cases some of the accessory minerals become rather 

 abundant, as sanidine, in many specimens, when the lava becomes a 

 Hanidine-leucite-rock : these are more highly silicated varieties. Augite, 

 although still an essential, becomes less abundant in the more recent 

 specimens. Altogether IG minerals are observed — leucite, nepheline, 



