554 Dr. Du Riche Preller — The Carrara Marble District. 



Another conclusion follows from the above-named close similarity of 

 the ground-masses : that the final consolidation, if the porphyroids are 

 intrusive, not extrusive, rocks, must have taken place within a com- 

 paratively short distance from the surface. Hence I believe that the 

 group on the whole is volcanic, and agree with the conclusions as to the 

 history of the district, which were so clearly and succinctly expressed 

 in 1911 by my late friend and old pupil, Mr. A. J. Jukes-Browne. 1 



As this paper has shown, I regretfully admit having made serious 

 mistakes about the origin of some of the Charnwood rocks. First in 

 time is that of supposing the Peldar and Sharpley porphyroids to have 

 been exceptional forms of altered tuffs, and then, after this had been 

 proved erroneous, in supposing the dominant Bardon rock to be 

 pyroclastic. In extenuation I may plead that in 1871, when Canon 

 Hill and I began our work in Charnwood, the microscopic study of 

 rocks was comparatively in its infancy, and that I was misled, prior 

 to the publication of our first paper in 1877, by an eminent foreign 

 petrologist, who had assured me that the porphyroids of the Ardennes 

 were not really igneous rocks (a statement for which I could find 

 no grounds on examining them in 1882 2 ). Also, that even ten years 

 later the effect of subsequent pressure on rocks of igneous origin was 

 not so well understood as it is at the present time ; and lastly, that 

 even now I have no hesitation in saying that these Charnwood rocks, 

 owing to their exceptional obscurity of structure, due in part to the 

 formation of secondary minerals, are more difficult than any with 

 which I have had to deal in a fairly wide experience. But I have 

 long been convinced that when one has made and published a mistake, 

 it is the wiser course to let this be known, lest it should continue to 

 mislead younger geologists. 3 



IV. — The Carrara, Massa, and Versilia Marble District. 



By C. S. Du Eiche Preller, M.A., Ph.D., M.I.E.E., F.G.S., F.R.S.E. 



I. Introductory. 

 rpHE range of the Apuan Alps, commonly called the Carrara 

 J. Mountains, is an offshoot of the Apennines, trending N.N.W. to 

 S.S.E., parallel to the Mediterranean littoral, from which it rises 

 within a distance of barely four miles to a maximum height of 

 6,000 feet above sea-level. Exclusive of the outer belt of the more 

 recent strata, the Triassic formation, within which the saccharoidal 



1 Building of the British Isles, p. 35. 



2 See Proceedings of the Geologists' Association, vol. ix, p. 247. 



3 It is only right to add that, after arriving at the conclusions stated in this 

 papsr, I found them to be substantially identical with those already reached by 

 Dr. F. W. Bennett and Dr. B. Stracey, of Leicester. To the one I am indebted 

 for helpful letters and copies of notes communicated to the Geologists' 

 Association, and to the other for kindly lending me some two dozen rock 

 slices from this north-western district, which, having been recently made in 

 Germany, were especially useful as being rather thinner than my own, of 

 English handiwork and for the most part at least a quarter of a century old. 

 It is fortunate that, as now the quarries are being so rapidly enlarged, they and 

 the Forest generally are being watched by such well-qualified observers as these 

 and other Leicester geologists'. 



