270 ANNUAL. OF SCIENTIFIC DISCOVERY. 



of the spring were intermittent, so that 10 or 20 years should elapse 

 between the periods when solid matter was emitted, or (say) an inter- 

 val of three centuries, as in the ease of Vesuvius between 1306 and 

 1631, the discharge would be on so grand a scale as to afford no mean 

 object of comparison with the intermittent outpourings of a volcano. 

 The Gases evolved from Hot Springs. Dr. 1) uibeny, after devoting 

 a month to the analysis of the Bath waters in 1833, ascertained that the 

 daily evolution of nitrogen gas amounted to no le.-s than 12-50 cubic feet 

 in volume. This gas, he remarks, is not onh characteristic of hot springs, 

 but is largely disengagt d from volcanic craters during eruptions. In both 

 cases he suggests that the nitrogen may be deiived from atmospheric air, 

 which is always dissolved in rain-water, and which, when this water pen- 

 etrates the earth's crust, must be carried down to great depths, so as to 

 reach the heated interior. When there it may be subjected to deoxy dating 

 processes, so that the nitrogen, being left in a free state, may be driven 

 upwards by the expansive force of heat and steam, or by hydrostatic 

 pressure. This theory has been very generally adopted, as best ac- 

 counting for the constant disengagement of large bodies of nitrogen, even 

 where the rocks through which the spring rises are crystalline and un- 

 fossiliferous. It will, however, of course be admitted, as Prof. Bischoff 

 has pointed out, that in some places organic matter has supplied a large 

 part of the nitrogen evolved. 



Carbonic-acid gas is another of the volatilized substances discharged 

 by the Bath waters. Dr. Gustav Bischoff, in the new edition of his val- 

 uable work on Chemical and Physical Geology, when speaking of the 

 exhalations of this gas, remarks that they are of universal occurrence, and 

 that they originate at great depths, becoming more abundant the deeper 

 we penetrate. He also observes that, when the silicates which enter so 

 largely into the composition of the oldest rocks are percolated by this 

 gas, they must be continually decomposed, and the carbonates formed by 

 the new combinations thence arising must often augment the volume of 

 the altered rocks. This increase of bulk, he says, mu-t sometimes give 

 rise to a mechanical force of expansion capable of uplifting the incumbent 

 crust of the earth ; and the same force may act laterally so as to compress, 

 dislocate, and tilt the strata on each side of a mass in which the new chem- 

 ical chan :es are developed . The calculations made by this eminent German 

 chemist, of the exact amount of distension which the origin of new mineral 

 products may cause, by adding to the volume of the rocks, deserve the 

 attention of geologists, as affording them aid in explaining those reiterated 

 oscillations of level, those risings and sinkings of land, which have oc- 

 cured on so grand a scale at successive periods of the past. There are, 

 probably, many distinct causes of such upward, downward, and lateral 

 movements, ami any new suggestion on this head is most welcome; but I 

 believe the expunsi >n and contraction of solid rocks, when they are alter- 

 nately heated and cooled, and the fusion and subsequent consolidation of 

 mineral masses, will continue to rank, as heretofore, as the most influential 

 causes of such movements. 



The temperature of the Bath waters varies in the different springs from 

 117 to 120 F. This, as before stated, is exceptionally high, when we 

 duly allow for the great distance of Bath from the nearest region of active 

 or recently extinct volcanoes and of violent earthquakes. The hot springs 

 of Aix-la-Chapelle have a much higher temperature, viz : 135 F., but 



