34 
THE GEOLOGIST. 
In publishing his Lectures on the Geolor/i/ of France, M. Lejeune does 
not pretend to have produced a book from liis 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, Avithout 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 alone 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 ; deer, rabbits, and wolves, to camels, 
lions, elephants, &c. ; whilst granite is grnnite in every clime ; amphi- 
bole, porphyry, and basalt are found to be identical from one pole to 
the other ; sand, clay, and limestone are everywhei'e similar. 
Georges Cuvier, however, 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 prosperity of a nation, its progress 
in civilization, and the whole detail of its manners and custom's. This 
is certainly saying enough of the importance of Geology and Mine- 
ralogy ; and we perceive that these beautiful sciences, so intimately 
connected with Ghemistry and Physics, attract more and more each 
day the attention of the admirers of Nature. 
Put to return to M. Lejeune. His book is not divided into very 
characteristic sections, except that he passes in succession from one 
geological massif 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 coimtry. We will analyse a few passages : — 
In speaking of I'Aveyi'on, our author relates that this part of France, 
bordering on the volcanic formations of Auvcrgne, presents to lis, not 
ancient volcanos which once upon a time vomited floods of lava, but 
hills of Goal-formation, whei'e, some centuries ago, damp air and spring- 
water occasioned the phenomenon of spontaneous combustion, which 
continues to the present day. Tliis combustion, kept up by the 
chemical change going on in the dccomi)osition of ii'on-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 Goal- 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 ; but, instead of producing the 
* The alum tlins produced is no doubt iron-alum, i.e. suli;>hate of iron and 
alumina, — T. L. ]'. 
