498 



ME. E. EUILEY ON THE EOCES 



rock, has been given by the liev. J. H. Timins (anal ysis xxxvii.* 

 This analysis is subjoined, together with one of eucrite lava from 

 Thjorsa in Iceland f : — 





Silica. 



Alumina. 



Iron 

 Oxides. 



Lime. 



Magnesia. 



Loss on 

 Ignition. 



Alkalies 

 and Loss. 





49-37 

 49-60 



15- 80 



16- 89 



10- 82 



11- 92 



11-90 

 13-07 



6- 40 



7- 56 



400 



2-59— 99-98 

 1-44—100-48 



Eucrite 



In the first analysis traces of oxides of manganese and copper are 

 recorded, and in the latter analysis traces of manganese, cobalt, 

 and nickel. In the latter analysis, also, the iron is all in the 

 protoxide condition, and the alkalies are given as Xa 2 0 = l , 24 and 

 K 2 O = 0-20. 



Mr. Timins J stated that the subject of his analysis contained a 

 few grains of olivine and a little quartz in cavities. He also adds, 

 " Parts of this rock resemble the matrix of the lava of the Capo di 

 Bove near Rome. In its chemical composition it nearly corresponds 

 with that which Bunsen gives for the ' Normal Augite ' § of 

 Iceland. Notwithstanding its occurrence in regular beds, its mine- 

 ralogical character and its chemical composition make it probable 

 that it has flowed over the surface." 



It is gratifying to find the mineral constitution of this rock, as 

 revealed by the microscope, so well in accord with the results of 

 Mr. Timins's analysis made twenty years ago. 



The rock is eucrite- or anorthite-basalt. 



The eucrite lava of Tbjorsa, the analysis of which I have here 

 employed for comparison, is cited by Yon Lasaulx || as an example 

 of a true eucrite, and there seems, therefore, good reason to accept the 

 analysis given by Kalkowsky as typical. The latter authority does 

 not consider the term eucrite well chosen, and deprecates its use. 



~Eo. 19. Herefordshire Beacon. East side, at the back of the Cave. — 

 Very fine-grained bluish-grey aphanitic rock. Under the microscope 

 it is seen to consist of felspars, chiefly labradorite, augite, titani- 

 ferous iron, leucoxene, and pyrites in exceedingly minute specks. 



The section is traversed by a small vein of epidote enveloping 

 fragments of the adjacent rock and also a little quartz. 



The augite appears in irregular grains, few distinctly formed 

 crystals being visible. 



The felspars occur in lath-shaped crystals, generally corroded and 

 frequently bent (PI. XXI. figs. 4 & 5). There is much opaque 



* " On the Chemical Geology of the Malvern Hills," Q. J. Gr. S. vol. xxiii. 

 p. 358. 



t Kalkowsky, ' Elemente der Lithologie,' Heidelberg, 1886, p. 130. 

 \ Op. cit. p. 359. 



§ The name Augite was used synonymously with Basalt by some of the 

 earlier writers, and is given, in this sense, by Kinahan, ' Handy-Book of Bo 

 Names,' London. 1873, p. 73. 



| ' Elemente der Petrographie,' Bonn, 1875, p. 316. 



