THE GEOLOGIST. 



In publishiiiii' bis Lectures: 07i the Geoloaj/ of France, M. Lejeime tloes 

 not preteud to have produced a book from his personal investigations, 

 but a work compiled from the best authorities, in which, however, the 

 author has been able to add, here and there, details of his own. 



It is now established beyond a doubt, that it is impossible to have 

 even a mediocre knowledge of any country, without being to a certain 

 extent a geologist. It is many years since Alexander von Humboldt, 

 in some of his admirable writings, made us familiar with the fact, that, 

 throughout Nature, rocks done show themselves identical in each 

 hemisphere, in every latitude. Passing from one climate to another, 

 we see. for instance, birch-trees, oaks, and maples, give place to palm- 

 trees, opuntias, and bamboos : Jeer, rabbits, and wolves, to camels, 

 lions, elephants. &c. ; whilst granite is granite in every clime ; amphi- 

 bole, porphyry, and basalt are found to be identical from one pole to 

 the other ; sand. clay, and limesrone are every\Yhere similar. 



Georges Cuvier. Ii0\vever, said one day. and with much truth, that 

 every mineral has its use, and upon its greater or less abundance in 

 such or such a place, or upon the greater or less facility with which it 

 can be extracted, often depends the p]'osperity of a nation, its progress 

 in civilization, and the whole detail of its manners and customs. This 

 is certainly saying enough of the importance of Geology and Mine- 

 ralogy ; and we perceive that these beautiful sciences, so intimately 

 connected with Chemistry and Physics, attract more and more each 

 day the attention of the admirers of Nature. 



But to return to M. Lejeune. His book is not divided into very 

 characteristic sections, except that he passes in succession from one 

 geological 7nasslf of France to another. It is rather a series of 

 chapters, written simply and clearly, each of which constitutes an 

 interesting excursion into some French province, or into some neigh- 

 bouring country. We will analyse a few passages : — 



In speaking of TAveyron, our author relates that this part of France, 

 bordering on the volcanic formations of Auvergne, presents to us, not 

 ancient volcanos which once upon a time vomited floods of lava, but 

 hills of Coal-formation, where, some centuries ago, damp air and spring- 

 water occasioned the phenomenon of spontaneous combustion, which 

 continues to the present day. This combustion, kept up by the 

 chemical change going on in the decomposition of iron-pyrites, the 

 formation of sulphate of iron, sulphate of alumina, &c. "produces 

 crystals of alum in such quantity as would supply with this substance 

 the entire wants of French industry.''* The conflagration going on in 

 these Coal-beds is hardly perceptible in the day-time; but in the dark- 

 ness of night one sees many little craters throwing up volumes of 

 vapour, the production of which is maintained by the water that 

 constantly filters through the soil. The people living near one of these 

 hills, hoping to extinguish the combustion, directed to the place all 

 the little rivulets of the neighbourhood j but, instead of producing the 



* Tlie ahmi thus produced is no doubt iron-ahnn, i.e. sulphate of iron and 

 alumina.— T. T. P. 



