476 Heriews — Guide to the Geological Gallery, Edinhurgh. 



expressed it, like a tilted 'pile of slices of bread and butter.' But as discovery 

 progressed the explanation of this arrangement soon became evident. The 

 formations revealed themselves as a series of what had originally been deposited as 

 horizontal sheets, lying in regular order one over the other, but which had been 

 subsequently bent up into alternating arches and troughs (i.e. the anticlines and 

 synclines of the geologist), their visible parts, which now constitute the surface 

 of our habitable lands, are simply those parts of the formations which are cut 

 by the irregular plane of the present earth's surface. All those parts of the 

 great arches and troughs formerly occurring alcove that plane have been removed by 

 denudation ; all those parts below that plane lie buried still out of sight within the 

 solid earth-crust. 



Although in every geological section of sufficient extent it was seen that the 

 anticline or arch never occurred without the syneline or trough — in other words, 

 that there was never a rise without a corresponding fall of the stratum. Yet it 

 is only of late years that the stratigraphical geologist has come clearly to recog- 

 nize the fact that the anticline and syneline must be considered together, and 

 must be united as a single crust-wave, for the arch is never present without its 

 complementary trough, and the two together constitute the tectonic, structural, 

 or orographic tinit, namely, The Fold, the study of which, so brilliantly in- 

 augurated by Heiin in his " Mechanismus der Gebirgsbildung, " is destined, I 

 believe, in time, to give us the clue to the laws which rule in the local elevation 

 and depression of the earth-crust, and furnish us with the means of discovery of 

 the occult causes that lie at the source of those superficial irregularities which 

 give to the face of our globe its variety, its beauty, and its babitability. — El>lT. 

 Gkol. Mag. 



12, E AT" I E AAT S. 



Edinburgh Museum of Science and Art Guide to the Geo- 

 logical Gallery. 8vo. Niel & Co., Edinburgli, and H. M. 

 Stationery Office, 1892. 



THE Science and Art Department having sanctioned the removal 

 of the Collection made by the Geological Survey of Scotland, 

 and its rearrangement in the Grand Museum of Science and Art in 

 Edinburgh, it can now be most advantageously studied. An exten- 

 sive gallery, the upper floor of the west wing, is devoted to the 

 exhibition of minerals, rocks, and fossils, not only those collected by 

 the Survey, but those given by Messrs. Dudgeon and Milne, Prof. 

 Heddle, Dr. Wilson, and others, and illustrative of the structure 

 and geological histor}' of Scotland, The rock-specimens are arranged, 

 together with the Geological Maps, as far as possible according to 

 their respective Counties ; and the rocks are most fully displayed 

 under the district where they are most typically represented, with 

 ample references, by means of numbers and otherwise, to the 

 localities. Descriptive labels for the petrology, geology, and topo- 

 graphy accompany the specimens. An index-collection of rock- 

 types is also at hand for the use of students. 



In the Guide here noticed, the order and contents of the cases 

 illustrative of the petrological geology of the several Counties of 

 Scotland are given in detail. The stratigraphical collection of 

 Scottish Fossils is similarly treated, but not so fully : and the 

 minerals are briefly noticed. Some geological models and photo- 

 graphs are also mentioned. 



The Department of Science and Art has to be congratulated on the 



