Correspondence — F. JSfopcsa—A. JSarker — S. S. Buckman. 95 



Dinosaurian, was preoccupied by Marsh for a crocodile (1871). 

 I therefore propose to name the Dinosaur mentioned (Noposa, 

 Denkschriften E. Akad. Wissensch. Wien, 1899) Telmatosaurus. 



Baron F. Noposa, Jun. 



Vienna, January Wth, 1903. 



GRANITE AND QUAETZ-VEINS. 



SiK, — The paper by Mr. J. Lomas on " Quartz Dykes near 

 Foxdale, Isle of Man," which appears in your January number 

 (p. 34), raises an interesting question, and presents the argument 

 in a cogent form. There can be no doubt that, on the fringe of 

 a granite intrusion and in its apophyses, we sometimes find a gradual 

 transition from normal granite, through various rocks which may 

 be termed pegmatite, greisen, etc., to pure vein-quartz. Some 

 phases of this transition are especially well displayed at Foxdale, 

 a locality which I have already cited in this connection (Q.J.G.S., 

 1895, vol. li, pp. 143, 144), and which has now been described in 

 detail by Mr. Lomas. 



Closer inquiry is, however, necessary before we can be waiTanted 

 in regarding such quartz-veins as igneous rooks in the ordinary 

 sense. There are many indications, both from the geological and 

 from the petrographical side, that the more siliceous products in 

 question, and especially the pure quartz-veins, belong at most to 

 the waning stage of igneous activity, when the temperature had 

 fallen and the agency of water had become a more important factor. 

 Dr. Sorby's well-known researches on fluid cavities, for instance, 

 strongly support this view (Q.J.G.S., 1858, vol. xiv, pp. 471-475). 

 But, further, there is sometimes reason to believe that, in these 

 highly quartzose fringes and veins in very intimate connection 

 with granite, a considerable part of the quartz has replaced felspar, 

 and is therefore not strictly a primary mineral. One very clear 

 example among others was described some years ago by Mr. Marr 

 and myself on the edge of the Shap granite (Q.J.G.S., 1891, 

 vol. xlvii, p. 285). Here distinct pseudomorphs of quartz after 

 felspar put the question beyond doubt. In the greisens of Cornwall 

 and Saxony, the beresite of the Urals, and such peculiar rocks as 

 luxulyanite and trowlesworthite, the occurrence of special ' pneu- 

 matolytic ' minerals like tin-stone, topaz, tourmaline, and fluor is 

 equally convincing. We must recognize the possibility of a like 

 origin for veins of quartz, or of quartz and mica, even where no 

 direct evidence of replacement is preserved ; and the existence of 

 an igneous magma composed of pure, or nearly pure, silica cannot 

 as yet be regarded as proved. Alfred Harkek. 



St. John's College, Cambkidge. 

 January 17th, 1903. 



THE TERM 'HEMERA.' 

 Sir, — Mr. Jukes-Browne seems to be haunted by the good word 

 stratigraphical.' In the January number he finds fault with my 



