192 ME. H. H. THOMAS 0^ THE [May I9II, 



of the felspars, by the less complete development of flow-structure, 

 and by assuming a more vesicular character. 



The olivine-bearing rocks show in the presence of olivine their 

 family resemblance to the marloesites (p. 198). They contain but 

 little fresh granular augite, sometimes none ; olivine, however, may 

 be represented by pseudomorphs of considerable size (fig. 7, B,p. 193) 

 in serpentine or chlorite. The ground -mass has a fine felsitic 

 or trachytic character, and is composed of minute albite-oligoclase 

 laths exhibiting a felted or fluidal arrangement. The felspar 

 phenocrysts are albite or albite-oligoclase. In common with the 

 marloesites (which see), these rocks often contain minute crystals 



iv. y. vi. 



Si0 2 58-47 61-01 5538 



Ti0 o 2-17 045 0-90 



A1 0, l 8- 60 18-45 1834 



Fe;0 3 1-92 209 1*13 



Feb ...= 4-77 0-80 5-86 



MnO 019 trace 



BaO 004 ... n. d. 



CaO 0-99 1-91 325 



MgO 094 0-94 3-47 



K o 330 4-75 0-22 



Na 2 5-52 733 712 



Li 2 trace ... n. d. 



H 0atl05°0 0-50 1 „ , Q 0-48 



H;0 above 105° C... 2\L9 J * u J 2-39 



P,0 5 0-45 ... trace 



C0 2 004 ... 200 



CI 002 ... n. d. 



Totals 100-11 100-82 100-54 



Anal E. G-. Eadley. Deicke. J. V. Elsden. 



IV= Soda-trachyte (lava), North Cliff of Skomer, opposite the Garland Stone 



[Anal. No. 347, E 7769], same rock as E 7122. 

 V=Soda- trachyte ? (block in tuff), Dachberg, Ehongebirge. H. S. 



Washington [after F. Einne], Prof. Paper 14, U.S. Geol. Surv. 1903 



pp. 396-97. 

 VI— -'Linie-bostonite.' Abercastle (North Pembrokeshire). J. V. Elsden 



Q. J. Cr. S. vol. lxi (1906) p. 596. 



and grains of a brown hornblende, similar to that detected by 

 Mr. Harker 1 in the mugearites of Skye. 



The hypersthene-bearing rocks (fig. 7, A, p. 193), or the Crabhall 

 type 2 of soda-trachyte, have a ground-mass like that already de- 

 scribed ; but it differs in the inclusion of fairly large, stained, and 

 striated prisms of apatite, and in the complete absence of granular 

 augite. The bastite-pseudomorphs after the rhombic pyroxene 

 measure up to 2 mm. in length, and the porphyritic albite-oligoclase 

 felspars up to 8 mm. The bastite is surrounded by an opaque 



1 'Tertiary Igneous Eocks of Skye ' Mem. Geol. Surv. 1904, p. 262. 

 3 J. J. H. Teall, ' British Petrography ' 1888, p. 284 [' a somewhat basic por- 

 phyrite oecurs at Crab Hole near Dale 'J. 



