394 THE CANADIAN NATURALIST. fOct. 



volume of the altered rocks. This increase of bulk, he says, must 

 sometimes give rise to 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 chemical changes are 

 developed. The calculations made by this eminent German chem- 

 ist of the exact amount of distention which the origjin ot new 

 mineral products may cause, by adding to the volume of tlie rocks, 

 deserve the attention of geologists, as affording them aid in explain- 

 ing those reiterated oscillations of level — those ri-ings and sink- 

 ings of land — which have occurred on so grand a scale at succes- 

 sive periods of the past. There are probably many distinct causes 

 of such upward, downward, and lateral movements, and any new 

 suggestion on this head is most welcome ; but I believe the expan- 

 sion and contraction of solid rocks, when they are alternately 

 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 IIT'^ to 120° F. This, as before stated, is excep- 

 tionally 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-Chapell.^ have 

 a much higher temperature, viz. 135"^ F., but they are situated 

 within forty miles of those cones and lava-streams of the Eifel 

 which, though they may have spent their force ages before the 

 earliest records of history, belong, nevertheless, to the most modern 

 geological period. Bath is about 400 miles distant from the same 

 part of Germany, and 440 from Auvergne — another volcanic 

 region, the latest eruptions of wdiich were geologically coeval with 

 those of the Eifel. When these two regions in France and Ger- 

 many were the theatres of frequent convulsions, we may well sup- 

 pose that England was often more rudely shaken than now ; and 

 such shocks as that of October last, the sound and rocking motion 

 of w4iich caused so great a sensation as it traversed the southern 

 part of the island, and seems to have been particularly violent in 

 Herefordshire, may be only a languid reminder to us of a force 

 of which the energy has been gradually dying out. 



But there are other characters in the structure of the earth's 

 crust more mysterious in their nature than the phenomena of 

 metalliferous veins, on which the study of hot-springs has thrown 



