| Page | |
| On the Pre-cambrian Rocks of the British Isles. | 1 |
| Are There Traces of Glacial Man in the Trenton Gravels? | 15 |
| Geology As a Part of a College Curriculum. | 38 |
| The Nature of the Englacial Drift of the Mississippi Basin. | 47 |
| Studies for Students. | 61 |
| Editorials. | 85 |
| Reviews. | 91 |
| Analytical Abstracts of Current Literature. | 95 |
| Acknowledgments. | 101 |
THE
JOURNAL OF GEOLOGY
JANUARY-FEBRUARY, 1893.
ON THE PRE-CAMBRIAN ROCKS OFTHE BRITISH ISLES.
During the last twenty years much has been written aboutthe "pre-Cambrian" rocks of the British Isles. Unfortunatelywhen attention began to be sedulously given to the study ofthese ancient formations, the problems of metamorphism werestill a hundred fold more obscure than they have since become;the aid of the microscope had not been seriously and systematicallyadopted for the investigation of the crystalline schists,and geologists generally were still under the belief that thebroad structure of these schists could be treated like those ofthe sedimentary rocks, and be determined by rapid traverses ofthe ground. We have now painfully discovered that these oldermethods of observation were extremely crude, and that the workperformed in accordance with them is now of little interest orvalue save as a historical warning to future generations of geologists.Geological literature has meanwhile been burdened withnumerous contributions which remain as a permanent incubus onour library shelves.
It may serve a useful purpose at the present time in possiblyaiding those who are engaged in the study of the oldest rocksof North America, if I place before them, as briefly as possible,the main facts which in my opinion have now been satisfactorilyproved regarding the corresponding rocks of Britain, and if Iindicate at the same time some of the more probable inferencesin those cases where the facts, at present known, do not warranta definite conclusion.
It is obvious that in any effort to establish that a group ofrocks is older than the very base of the sedimentary fossiliferousformations, we must somewhere find that group emerging fromunder the bottom of these formations. Until lithological charactersare ascertained to