482 DE. A. JOWETT ON THE [Oct. I913,. 



EXPLANATION OF PLATES XLV & XLVI. 



Plate XLV. 



[Illustrating the relations between the lavas and the sediments.] 



Fig. 1. Cliff-section south of Kirk Loch. The compact lava at the base- 

 becomes increasingly fissured, and passes into loose blocks above. 

 All the fissures and the spaces between the blocks are filled with 

 fine sediment. The section shows about 8 feet vertically. 



2. Horizontal and vertical section on the s-hore south of Rock Skelly. 



A network of sandstone-filled fissures is shown in plan in the 

 foreground. The handle of the hammer rests against a mass of 

 sandstone which is partly horizontal and partly almost vertical. 



3. Stack on the shore in Kirk Loch. Vertical height = about 12 feet. 



Horizontal lenticular beds of sandstone 3 to 6 inches thick among 

 the lava near the base of the section. 



4. Cavity in lava partly filled by sediment ; at the base of a cliff east of 



Dunninald Den. The stratification of the sediment in the lower 

 part of the cavity is undisturbed; above, the layers of sediment are 

 broken, and amygdales appear (see PI. XLVI, fig. 6). At the top of 

 the figure, amygdaloidal sediment may be seen entirely filling another- 

 cavity. 



Plate XLVI. 

 [Microphotographs of rocks from the Forfarshire coast.] 



Fig. 1. Enstatite-oliviue-basalt, near Montroseness. Phenocrysts 01 labradorite 

 and fresh enstatite. Olivine, labradorite, granular augite, magnetite, 

 and dusty interstitial glass in the ground-mass. The olivine occurs- 

 as serpentinous pseudomorphs with borders of haematite. X20. 



2. Enstatite-basalt, south-west of Fishtown of Usan. Phenocrysts of 



basic labradorite and bastite pseudomorphs after rhombic pyroxene 

 in a glassy ground-mass full of magnetite dust, with felspar microlites. 

 Interesting intergrowths of felspar and pyroxene occur. X20. 



3. Olivine-basalt (normal type) on the shore south of Rock Skelly. Pseudo- 



morphs in serpentine and haematite after olivine-phenocrysts. The 

 ground-mass shows microporphyritic labradorite, augite, magnetite, 

 and interstitial glass. X-U. 



4. Olivine-basalt east of Ethie Haven. Normal type, with holocrystalline- 



ground-mass. Minerals as in fig. 3. X20. 



5. Glomeroporphyritic olivine-basalt, South Mains Quarry, Ethie. The- 



glomeroporphyritic aggregates contain olivine (serpentine and 

 haematite pseudomorphs), twinned augite, and labradorite. Felspar, 

 granular augite, iron-oxides, and a little interstitial glass occur in the- 

 ground-mass, which indicates' flow-structure. This type is on the 

 whole less basic than usual. X20. 



6. Amygdaloidal sandstone from a cavity iu lava east of Dunninald Den 



(PI. XLV, fig. 4). The finer layers of sediment appear to have broken, 

 up while the coarser sediment was still unconsolidated. The 

 amygdales contain chlorite and calcite. X6. 



Discussion. 



Dr. J. W. Evans remarked on the interest of the paper and on- 

 the clearness with which the Author had placed the facts and his 

 conclusions from them before the Society. It was remarkable 

 that the Lower Old Red Sandstone lavas of this area should be so 

 much more basic than tho.se of the Cheviots. The speaker was still 

 inclined to believe that many of the conglomerates were due ta 



