84 HISTORY OF GEOLOGY AND PAL/EONTOLOGY. 



composed of granite, and whose outer layers comprise 

 porphyry and the primitive rocks. This crude conception of 

 Heim's has certain points of analogy with the much later 

 theory of " central massives " promulgated by mountain 

 geologists. 



Heim sub-divided the sedimentary or stratified deposits in 

 four main groups as follows : 



4. Newer limestone, including Muschelkalk and Jurassic 

 limestones. 



3. "Bunter" or variegated sandstone (including the sand- 

 stone of Fiichsel). 



2. Older limestone or Upper Dyas ("Zechstein" of Leh- 

 mann). 



i. Red Underlyer or Lower Dyas ("Rothe Todtliegende " 

 of Lehmann). 



He also made a special inquiry into the origin and distribu- 

 tion of basalt, and wrote strongly in favour of its eruptive 

 origin. He regarded it as younger than all four sub-divisions 

 of the sedimentary deposits, and supposed that its eruption 

 had been accompanied by violent crust-movements, during 

 which the rocks were bent and fractured and the mountain- 

 systems were upheaved. 



The subjects of denudation and erosion also attracted 

 Heim's attention, and he gave a full description of the erosion 

 of valleys by the agency of running water, enumerating many 

 good examples in confirmation of his ideas ("On the Forma- 

 tion of Valleys," Voigfs Magazine^ 1791). 



One of the most loyal and gifted of Werner's scholars was 

 Johann Karl Freiesleben (1774-1846). He was born and 

 educated at Freiberg, and enjoyed the intimate companion- 

 ship of his master and patron. While attending Werner's 

 classes he formed the friendship of Von Hum bold t, Von 

 Buch, and Von Schlotheim; he afterwards travelled with Buch 

 in Saxony, with Schlotheim in Thuringia, and with Hum- 

 boldt in the Bohemian mountains, the Alps, and the Swiss 

 Jura mountains. 



His first large work, 'Description of the Harz Afountains 

 (2 vols., 1799), contains chiefly mineralogical and technical 

 information, and a later work, Contributions to the Mineral- 

 ogical Knowledge of Saxony ', published in 1817, is of the same 

 nature. 



As a geologist, Freiesleben accomplished memorable work 



