MINERAL SPRINGS. •'537 



Iodine, Lithium, Strontium, Copper, and some organic matter are likewise present. 

 Dr. Daubeny ascertained that the daily evolution of ^nitrogen gas amounts to 250 

 cubic feet in volume ; carbonic-acid gas is also given off, as vi^ell as a small 

 amount of oxygen. 



The waters unquestionably rise from a great depth ; they have been tapped 

 at about the junction of the Keuper and Rhsetic beds, and there is no doubt that 

 they spring through faults or fissures in the subjacent Carboniferous rocks, as was 

 originally suggested by William Smith. Regarding them as natural artesian wells, 

 Prof. Prestwich calculates from their temperature that the depth from which they 

 rise is about 3500 feet ; in this case they may be supported by the Lower Lime- 

 stone Shales.^ 



Referring to the large quantity of nitrogen gas constantly being disengaged, 

 Dr. Daubeny has remarked that the same gas is freely evolved from most thermal 

 springs, the majority of which are associated with volcanoes, and that it is like- 

 wise evolved from volcanoes, both in an active and a dormant condition. The 

 Bath springs, in his opinion, were therefore probably connected in some manner 

 with the cause of volcanic action ; and Prof. Judd has remarked that they relieve 

 the earth's crust of an amount of heat, perhaps equal to that of a considerable 

 volcano. The study of the Bath springs opens up a number of interesting questions, 

 for while the mineral ingredients of these and other springs is due in great measure 

 to the presence of some of them in the i"Ocks through which the waters pass ; yet, 

 at the same time, as Sir Charles Lyell observed, mineral springs may derive an 

 inexhaustible supply, through rents and porous rocks, from the leaky bed of the 

 ocean. Nor is this theory unreasonable, if we believe that the contiguity of nearly 

 all the active volcanoes to the sea is connected with the access of salt-water to the 

 subterranean foci of volcanic heat.^ 



The composition of sea-water from the Channel is as follows : ^ — 



Grains per 

 Imp. Gallon. 



Chloride of sodium I964'i6 



Chloride of potassium ^5'3I 



Sulphate of lime gS'^G 



Carbonate of lime 2 "31 



Chloride of magnesium 256'66 



Sulphate of magnesia l6o'70 



Bromide of magnesia 2 "05 



Iodine. ..r traces 



Ammonia traces 



2499-65 



The components of sea-water are to a large extent original (see p. 2), but 

 many ingredients are brought in by rivers, etc. Moreover, it is interesting to note 

 that Forchhammer has detected silver, copper, and lead in Corals ; copper, zinc, and 

 iron in the ashes of Sea-weeds ; cobalt and manganese in the Sea-wrack {Zostera 

 niarhta) ; and cobalt in fossil Sponges from the Chalk. These observations are 

 in a measure confirmed by Mr. John Murray, who states that almost every 

 element is contained in sea-water, many of them, however, in exceedingly minute 

 quantities.* 



The possible influence of sea-water on our underground waters is indeed a 

 subject of the greatest importance, especially as we find chloride of sodium in 



^ Q. J. xlii. 305 ; Prestwich, Geology, Chemical and Physical, p. 166. 

 ^ See Daubeny, Remarks on Thermal Springs and their connection with 

 Volcanoes, 1832; Lyell, Address to Brit. Assoc. 1864; Judd, Volcanoes, 

 p. 219. 



■ 3 Schweitzer, Phil. Mag. 1839, xv. 58 ; G. Forchhammer, Phil. Trans. 1865, 

 ■p. 203. 



•* Nature, Oct. 15, 1885, p. 583. 



