Prof. T. G. Bonney — Foliation mid Meiamorphism. 197 



as I believe it to be, of its gneisses and hornblende schists came home 

 to me. The same holds good of the Alps, but in one paper relating 

 to them, that on The Carboniferous Gneiss at Guttannen, 1 I doubt if 

 I have not fallen into one error while trying to correct another. 

 Besides studying the slab supposed to contain two small tree stems 

 in the Berne Museum, I visited Guttannen in 1891, 1895, and 1897, 

 and in the last year saw an outcrop of the " Carboniferous gneiss" 

 in the Urbach-thal. But it has since been proved that these 

 objects are not fossils of any kind. 2 



HOW THE PROBLEMS AROSE. 



On beginning to give lectures in Geology just half a century ago, 

 I soon discovered how little I knew about that part of it which is 

 now called petrology, and that the authors of the textbooks then 

 in use were in much the same position. In England Be la Beche, 

 in Scotland Macculloch 3 had done most valuable work, but with 

 their deaths not only had progress been arrested but also 

 a movement had begun in a reverse direction. 



The application of the microscope to the study of thin slices of 

 rocks, for which we are indebted to the inventive genius of 

 H. C. Sorby, 4 arrested this movement and gave the student a surer 

 footing. I began to work with this instrument about 1870 

 (tentatively at first, because at that time my eyes were far from 

 strong), and for a while restricted myself to the igneous rocks, but 

 I was soon drawn into those of the metamorphic group and was 

 speedily confronted by statements which, as I was not long in 

 finding, rested on very uncertain evidence. This forced me to 

 enlarge my field of examination. Charnwood, as I have said, soon 

 presented one set of problems, the Lizard another. The difficulties 

 of the Llanberis district resembled the former, those of Anglesey 

 to some extent approximated to the latter. Specimens sent to me 

 by friends directed my attention to the alleged metamorphism in 

 South-Western Ayrshire and in the North-Western Highlands, and 

 I sought light on the difficulties of the latter by studying the 

 gneisses and schists of the Alps, among which I often spent 

 a summer holiday. 



Thus having done what I could, for nearly forty years, by work 

 in the field and with the microscope, to solve some of the problems 

 presented by the metamorphic rocks, I have thought that perhaps 

 a short record of the results might be useful. It contains, I fear, 

 nothing new; probably everything in the following pages "has 

 been said by somebody somewhere ", but I may at any rate plead 

 that my conclusions have not been taken "second-hand". As a rule, 



1 Q.J.G.S. xlviii, p. 390. 



2 The story of this " Comedy of Errors " is told in " Plant Stems in the 

 Guttannen Gneiss ", Geol. Mag. 1900, p. 215. 



3 J. Macculloch died in 1835, H. T. De la Beche in 1855, but the clouds 

 were gathering again before the latter date. An excellent account of the 

 difficulties which had to be encountered by those who were living and working 

 in the earlier half of the nineteenth century is given by Sir A. Geikie in The 

 Founders of Geology, ch. viii. 



4 He began this work, for some years little appreciated, about 1850. 



