2i8 SOME NEW BOOKS [September 



the Gallery devoted to Scottish Mineralogy and Geology in the Edinburgh 

 Museum of Science and Art. 



It is no easy matter to give a summary of the contents of a book which 

 contains in a highly-condensed (though perfectly lucid) form, so enormous an 

 accumulation of facts. To the readers of Natural Science probably the chief 

 interest of the work will centre upon the palaeontological portion, and upon 

 such parts of the work as are more or less directly concerned with the Life of 

 the Past ; but we may, nevertheless, briefly notice its contents as a whole : — 



The earlier chapters of the history bring before us records of a submarine 

 volcanic episode, during the latter part of which the chief organic remains 

 which were entombed in the sediments belonged to the Tetragraptidae, Phyllo- 

 graptidae, and a few other Arenig forms of graptolites, together with one or 

 two Phylloped Crustacea, and a few Inarticulata, representing the Brachiopoda. 

 Next follows a record of much deeper water conditions, during which a large 

 area of what is now Southern Scotland would appear to have lain at the 

 bottom of an ocean more than 2500 fathoms in depth. It was at this time 

 that the now well-known Arenig Radiolarian Chert was formed. (It may not 

 be generally known that Mr. Peach was really the first to recognise the true 

 nature of this deposit, and that named specimens of it were exhibited in the 

 Gallery of Scottish Geology and Mineralogy in Edinburgh a year or more 

 before any published description appeared.) Following this ancient oceanic 

 ooze comes a record of frecpient oscillations of level, and of a gradual elevation of 

 at least the western part of the district to above the level of the waves. In 

 the meantime the Arenig forms of graptolites had died out, new generations 

 of Rhabdophora had gradually come into being, and the conditions favourable 

 for the evolution of group after group of new species and genera appear to 

 have continued, in certain areas, as around Moffat, for an interval of time of 

 incalculable length. Then follows another and lengthy period, during which 

 we have perfectly clear evidence, in other areas, of the gradual appearance and 

 disappearance of whole families of Coelentera, Brachiopoda, Trilobita, and 

 Arthropoda, as well as of other organisms ; and evidently also (although the 

 earlier chapters of this part of the history are yet wanting) of the gradual 

 evolution of the ancestral forms of the Vertebrata. One of the most interesting 

 features in the book is the record of the discovery of fish remains in the higher 

 beds of the Silurian Rocks. These fossils have already enabled Dr. Traquair 

 to throw a flood of light upon some points that had previously remained in 

 obscurity ; and there can be little doubt that we shall shortly learn more still, 

 as the beds that yielded these organisms continue to be diligently searched. 

 The closing episode of the Silurian Period in Scotland was one in which the 

 marine conditions which had so long endured gradually came to an end. 

 Continental conditions took the place of oceanic, terrestrial volcanoes arose 

 upon what had formerly been the sea-bottom, and the Silurian sea finally gave 

 place to the deserts within which the Old Red Sandstone was formed. 



It is chiefly in connection with the eruptive and metamorphic rocks which 

 date from this Devonian period, that Mr. TealPs numerous and valuable contri- 

 butions have been given. Like the Stratigraphical and the Palaeontological 

 parts of the book this Petrographical part cannot be summarised, for the simple 

 reason that, from beginning to end, the work is already as closely condensed as 

 it can possibly be. 



Regarding the book as a whole one may confidently state that it is the 

 finest geological monograph that has yet appeared, at home or abroad, and 

 that it reflects the highest credit upon every one concerned in its production. 



J. G. G. 



