814 REPORT—1890. 
feature is an abundant brown mica, dispersed through the rock in lustrous plates. 
In some cases these are of considerable size; in most of the rocks, however, they 
sink to minute specks, which are present in considerable number and give the rock 
a glittering appearance. 
These notes are based on work done by the author for the Geological Survey, 
The specimens were collected by Mr. Strahan and himself in the summer of this 
year, and full details of their investigations will be published in the Survey Me- 
moir on Sheet 97, N.W., now in course of publication. Sections for the microscope 
were made from dykes in the following localities: Backside Beck, west of the vol- 
canic series ; dyke in Wattle Gill; dyke in the Rawthey at Ward’s Intack ; dyke in 
Taith’s Gill, 200 yards north of Fox Hole Rigg; dyke in Backside Beck, 100 yards 
north of the Wandale Fault ; dyke at base of first felsite, Backside Beck; dyke 
near the foot of Wattle Gill; dyke in shale near the topmost felsite, Wattle Gull ; 
dyke 300 yards west of Rawthey Bridge. 
Under the microscope the mica sometimes appears in regular six-sided plates, 
but more frequently in ragged patches and blades. It is a dark-brown biotite, 
probably meroxene. Penetrating the mica, fine needles of apatite are often to be 
observed. 
Another striking feature in these rocks is the presence of carbonate of lime in 
considerable quantity. In many cases they are so highly charged with calcite as 
to effervesce freely with acid. This mineral has completely replaced the original 
constituents of the rock, forming pseudomorphs, the shape of which gives some 
indication of the nature of the replaced mineral, Augite has doubtless been 
replaced in this way, and the shapes of some of the calcite pseudomorphs clearly 
point to olivine having been an original accessory constituent of these rocks. The 
felspar (orthoclase) is surprisingly small in quantity, being confined to small 
microlites and interstitial patches in the groundmass, but the latter is generally so 
obscured by calcite dust and stained by oxide of iron that even this can only be 
made out after dissolving away the carbonate of lime from the section with dilute 
acid. Chlorite is also present in patches and scattered fibres. In part this 
mineral is no doubt derived from the decomposition of the biotite, in part also from 
the augite. Magnetite is present in scattered granules. 
3. Note on Phillips’s Dyke, Ingieton. By Tuomas Tats, F.G.S. 
The author stated that visitors to Ingleborough could examine an interesting 
mica-trap, the only one of the numerous West Yorkshire dykes described by 
Phillips in his classical work (‘ Yorkshire Geology,’ Part II., Mountain Limestone, 
p. 85, 1835). 
Intrusive in Coniston calcareous shales, north of the Cravenfault, it projects as 
a nearly vertical dyke from the east bank of the Doe, three hundred yards above 
the Catleap waterfall, Storrs, Ingleton. 
Macroscopically it is a flesh-coloured matrix, fine-grained, and of uniform 
texture, enclosing porphyritic crystal groups of somewhat larger felspar crystals 
surrounded by a framework of brown mica. 
The microscopic sections (exhibited) reveal a holocrystalline ground mass, of 
which orthoclase, hornblende, and biotite are the chief components, the latter 
mineral alone presenting idiomorphic contours. 
Two generations of felspar; small crystals of uniform size diffused through, 
and originally the main constituents of, the ground-mass; and larger crystals in 
glomero-porphyritic clusters, each enclosed by magnesian mica generated around 
it, repeat the peculiar structure seen in hand specimens. The rock is a Mica- 
syenite or Minette, the best preserved of all the West Yorkshire traps. 
4, Sixth Report on the Volcanic Phenomena of Veswvius.—See 
Reports, p. 397. 
