466 Pf'of. Buck/and on the Structure of the Alps, [June^J 



Primitive Rocks. 



It may be useful to add to this table of geological equivalents ^ 

 a list of those alpine formations which most nearly resemble 

 each other, and which it is nevertheless very important to dis- 

 tinguish ; e. g. there are in the alpine districts four varieties of 

 conglomerate, four of gypsum, and five of dolomite. 



Co7ighmerates, 4. 



1. The most ancient of these conglomerates is that of the '• 

 petit St. Bernard, the Vallorsine, and Tarentaise, being a true 

 transition rock, and containing rolled fragments of granite, mica 

 slate, gneiss, quartz rock, and primitive limestone. 



2. The next in point of age is that of Schwanden and Mells 

 near Glarus, and Mount Neisen on Lake Thun, being of the 

 same era with the old red sandstone (rothe todte liegende) of 

 Werner, and new red conglomerate of England. 



3. The third and most abundant conglomerate is that which, 

 under the name of nagelflueandRigi puddingstone, extends along 

 the line of junction of the Great Swiss Valley with the alpine 

 limestones from Vevey on the Lake of Geneva to Bregentz on 

 the Lake of Constance, and thence continues onwards along the 

 edge of the plain of Bavaria towards Saltzburg. This is the 

 most recent of the stratified rocks of this district, and is nearly 

 of the same age with the Hertfordshire puddingstone of England. 



4. The fourth, which is also called nagelflue, consists of agglu- 

 tinated masses of diluvian gravel, composed chiefly of pebbles 

 of alpine limestone, and not to be distinguished but by the cir- 

 cumstances of its position from No. 3. It is usually found in the 

 valleys, and in irregular patches on the lower hills, while No. 3 

 forms a chain of mountains from 3000 to 4090 feet high, which 

 is continuous through nearly the whole of Switzerland. No. 4 

 abounds in all the diluvium of Switzerland, Tyrol, and Italy, 

 when the pebbles are calcareous. It should seem these pebbles 

 have supplied the cement by which they are held together, as the 

 <^ravel is usually loose when composed of any other substance 

 than limestone. 



Gi/psum Formations, 4. 



In the same districts we have certainly three, probably four, 

 formations of gypsum. 



1. Primitive. 2. Transition. 3. Secondary. 4. Tertiary. 



1. Primitive. — Existing in small quantities (if at all) in the 

 Alps.^ Brochant and D'Aubuisson doubt whether there be here 

 any true primitive gypsum, and are inclined to class that which 

 has been considered primitive among the transition series. 



2. Transition Gypsum. — Much of this occurs among the tran- 

 sition rocks of the Tarentaise described by Brochant. It may 



