i-drogen. 



Oxygen. 



5-25 



42 10 



5-46 



28-13 



3-38 



2-58 



CIV mOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Carbon. 



Woody fibre 52-65 



Brown coal 66-41 



Anthracite (Welsh) . 94-04 

 And after describing the mode of formation of the bed of clay or 

 chalk which generally underlies a Carboniferous deposit, he shows 

 that in those old periods the atmosphere must have contained a 

 much larger proportion of carbonic acid gas than now, a favourable 

 circumstance for the growth of plants, but injurious to that of air- 

 breathing animals, and he suggests that by the deposit of the 

 carbon in the earth, the air was purified and prepared for the growth 

 of a higher class of animal life. 



Although Switzerland itself is ill provided with coal, there is 

 enough to show that even in these early days of our planet a con- 

 tinent must have existed towards the line of the Central Alps, and 

 that it was clothed with vegetation. The rocks, however, which 

 contain its remains have been so often disturbed by the convulsions 

 which have repeatedly altered the appearance of the country, that 

 they now form a portion of the loftiest mountains of Switzerland. 

 They are in many places so caught-up and buried amidst younger 

 rocks, that several distinguished geologists have been thereby 

 deceived, and have attributed to them too recent a date. 



Dr. Heer then endeavours to form some calculation as to the 

 length of time during which the Coal-period lasted ; and after calcu- 

 lating the average annual growtli of peat-moors, and the thickness 

 of peat necessary to form a given thickness of coal, he comes to the 

 conclusion that a bed of coal 44 feet thick would have required 

 20,000 years for its formation. Probably, however, under more 

 favourable circiunstances the growth of the peat was more rapid 

 than at present ; at the same time, however, it must not be for- 

 gotten that, in calculating its age, the beds of sandstone, clay, and 

 limestone which accompany the coal must also be considered, and 

 these are of enormous thickness in some places. In Switzerland 

 alone the carboniferous beds have occasionally a thickness of 6000 

 and 7000 feet. What an enormou s period of comparative quiet they 

 represent ! 



But this period of calm was at length disturbed by convulsions 

 which introduced the Permian period, cliaracterized in many parts 

 of Germany by vast deposits of red sandstone, and in many places 

 by outbursts of porphyritic and other igneous rocks. Prof. Heer 

 also observes that this formation is remarkable for containing 

 most of the copper which has been obtained both in Europe and in 

 North America. 



The second chapter is devoted to an account of the formation 

 of salt-deposits in Switzerland, and to a description of the Triassic 

 rocks, consisting of Bunter Sandstein, Muschelkalk, and Keuper. 

 He alludes to the occvirrence of the Avictila-contortaheds in some 

 parts of Switzerland, and refers them to the upper beds of the Keu- 

 per, with which he thinks their fossils have the greatest analogy. 



The third chapter is devoted to the Lias formation, and com- 



