THE CHEMISTRY OF UNDERGROUND WATERS. 817 



ores of copper and tinwliicbtbe miner's operations bad taken from ber, 

 and from wbicb tbe furnaces of tbe metallurgists bad laboriously ex- 

 tracted tbe two metals of bronze. 



Lead pipes, of wbicb tbere were a great number in connection witb 

 a wbite marble piscina, bad suffered a no less energetic alteration. 

 Tbey were deeply corroded and perforated, and bad by solution formed 

 minerals witb bases of lead — tbe sulpburet, or galena, and tbe cbloro- 

 carbonate, or pbosgenite. 



Among tbe iron compounds tbe bisulpburet, or j^yrites, is of special 

 interest, on account of its abundance in tbe crust of tbe eartb. At 

 Bourbonne, and in tbe basins of otber tbermal springs at Aix-la- 

 Cbapelle, Bourbon-Lancy, Bourbon-l'Arcbambault, and Saint-Nectaire, 

 pyrites bas been detected in course of formation, but only in tbe 

 deeper parts of tbe basin remote from atmospberic oxygen. 



In view of tbese cbanges, wrougbt by tbermal water on inorganic 

 bodies, it is not surprising tbat tbe same agent sbould also act upon 

 organic bodies. Tbe wood of tbe piles supporting a masonry-work, 

 wbile it bas perfectly preserved its texture, bas become bard and beavy 

 witb tbe mineral matter wbicb it bas absorbed. Tbe original sub- 

 stance bas almost disappeared, and given place to carbonate of lime, 

 wbicb bas penetrated, as tbe miscroscope sbows, to tbe most minute 

 interstices of tbe vegetable cells. 



Tbese sj)rings of Bourbonne bave given rise, witbin a very limited 

 space, to not less tban twenty-four species of crystalline minerals, in 

 combinations wbicb, accumulated and grouped as tbey are, closely re- 

 semble tbe ancient metalliferous beds — in detail as well as in general. 



Otber evidences of tbe mineralizing power of thermal waters have 

 been exhibited in their operation for considerable distances below 

 tbe surface of the ground. Penetrating the subsoil at Plombieres, 

 they have since the Roman period engendered a series of species no 

 less remarkable than the preceding series, although they did not at- 

 tract attention by a metallic luster ; they are silicates of the zeolite 

 group, opal, and chalcedony. When we tiy to apply the experi- 

 mental method to the reproduction of geological phenomena, we are 

 met, among otber difficulties, by the brevity of human life, which is 

 very short in comparison with the immense periods which have pre- 

 sided over the formation of tbe crust of tbe earth. Such facts as 

 these, fortunately, make up for this inability, and put us in the pres- 

 ence of experiments that are forbidden to our laboratories, from which 

 we learn what can be effected by very weak actions prolonged through 

 ages. By these synthetic demonstrations, carried on during twenty 

 times the duration of human life. Nature teaches us tbat she is still 

 employing processes similar to those which she used in the most re- 

 mote epochs. 



We come now to see how subterranean waters obtain a beat which 

 makes them thermal springs, and which connects them by intermediate 

 VOL. XXXII. — 52 



