Reviews—Daubrée’s Subterranean Waters. 39 
and having a bed of serpentine interposed between the two Tertiary 
deposits. The pipes supplying the soffionis are represented as 
cutting across the several formations, but no suggestion as to their 
primary source is offered. With respect to volcanoes, M. Daubrée 
observes that in spite of the idea which they suggest generally of 
melted rocks originating in the dry way (voie ignée)), before all 
things they represent supplies of water, since everywhere the vapour 
of water is one of the principal products of their activity. An 
effective cnt of the explosion of Krakatau helps to illustrate this. 
Book II. supplies us with some valuable facts relative to the 
temperature both of cold and hot springs. 
Book III. deals with the composition of underground waters, 
First of all theauthorenumerates the substances dissolved or chemically 
deposited by them. Speaking generally, one may say that nearly all 
the elements or their primary compounds exist dissolved in water 
somewhere, either with or without the aid of other solvents; but 
sulphur, silica, and carbonate of lime are amongst the most abundant 
deposits. By way of illustration Mons. Daubrée gives a photograph 
of the mud springs with sulphur at Crater Hill after Hayden, and 
many other pictorial representations of silica and limestone deposits, 
taken from various quarters of the globe. Most of these are nowin 
full operation. Compounds of aluminium are rare; nevertheless the 
hydrous silicates of that mineral, such as allophane, are still being 
deposited. With respect to the classification of mineral waters Mons. 
Daubrée will not admit of any preconceived ideas: the predomi- 
nating substances must decide the grouping. The families are 
classified according to the principal electro-negative element, as 
chlorides, sulphides, sulphates, carbonates and silicates: the genera 
by the principal electro-positive (basic) element, as sodic, calcic, 
magnesic, ete. Under such an arrangement the waters of the Old 
Sulphur Well at Harrogate, which is a “strong saline sulphur” 
containing about 1000 grains of haloid salts to the gallon, would be 
classified as a brine, in spite of its free hydrogen sulphide and its 
five grains per gallon of sodium sulphydrate appealing alike to the 
taste and smell. At the same time it is not easy to say where Mons. 
Daubrée would draw the line, since he cites a spring at Baréges as a 
sulphur water which contains 0-04 grms. of sulphide of sodium to 
the litre out of 0-11 grms. of fixed substances, i.e. rather more 
than one-third. This is what would be called a “pure sulphur 
water ” in the language of the Harrogate doctors. 
The silicated waters (sources silicatées), as Mons. Daubrée justly 
observes, are of the highest interest to the geologist. The silica 
would usually seem to be in combination with soda, but weighable 
quantities of the silicates of lime, magnesia and alumina have been 
found in a water of the Hautes-Pyrénées. 
After glancing at the reactions of underground waters on the 
material bathed by them, the author proceeds to consider the origin 
of the substances dissolved in the water or chemically deposited by 
them. Amongst the most obvious are the filth of cities draining 
into rivers and contaminating the waters of shallow wells; then 
