1317.J Geological Society. 471 
a mactra, the cast of a large serpula, and other shells which bear 
a great resemblance to those found in the calcaire grossiere of Paris. 
The reading of Dr. Berger’s paper, entitled, Geognostic Remarks 
on the Rocks in the immediate Vicinity of Dublin, was concluded. 
The oldest rock in the immediate vicinity of Dublin is grey- 
wacke, Nearly the entire promontory of Howth is composed of 
this rock in all its varieties, interstratified with subordinate beds 
of clay-slate. The mean dip of the beds is about south-east, at an 
angle of 38°. Besides the clay-slate, other subordinate beds occur 
in this formation, such as flinty-slate in the island called Ireland’s 
Eye, and compact porphyritic felspar on Rathcoote Common, Of 
the floetz rocks, the oldest is a shell lime-stone, from which all the 
lime in the neighbourhood of Dublin is procured. It is chiefly cha- 
racterized by encrinital remains and the anomia producta. It dips 
SE by S, at a mean angle of 45°.’ A magnesian lime-stone alter- 
nating with beds of shelly and clayey lime-stone appears to rest on 
the encrinital lime-stone. It dips nearly SW, at an angle of about 
27°. The Calp lime-stone, or Luilding-stone, is the next in suc- 
cession, and occupies by far the greatest part of the district here 
described. It consists of many beds, and contains the five follow- 
ing varieties of rock. 1. Building-stone, in beds of from 18 inches 
to 21 feet thick, and of remarkably regular stratification. Its colour 
is grey, approaching to black. When rubbed, it gives an odour of 
sulphureted hydrogen. It burns white, but does not form a good 
quicklime, nor does it contain any organic remains. 2. Flags, 
‘These are beds more or less slaty, which intervene between the beds 
of building-stone. They are of a more earthy texture than the 
latter, and contain spangles of mica. ‘Their thickness varies from 
three inches to one foot. %. Lime-stone, in beds rarely less than 
three feet thick. It contains no organic remains; and, not being 
recognized by the quarrymen as a lime-stone, is made no use of. 
4. Wallers, or ashlers. The beds to which this name is given are 
of an extremely dense close texture, and of a blue colour. 5. Black 
Jlint, or chert, in continuous layers, one or two inches thick, The 
general dip of the Calp formation is nearly due S. at an angle 
of 19°, 
Dec. 6.—The reading of a paper from Mr. Phillips, entitled, On 
the Forms and Measurements by the reflecting Goniometer of cer- 
tain primitive Crystals, with Observations on the Method of obtain- 
ing them by mechanical Division, was begun. 
Dec. 20.—At this meeting the reading of Mr. Phillips’s paper 
was concluded. 
The substances noticed in this paper are oxide of tin, sulphate of 
barytes, quartz, zircon, staurotite, anataze, specular iron, diopside, 
eyanite, corundum, sulphate of strontian, carbonate of lead, sul- 
phate of lead, blue carbonate of copper. 
The crystallographical history of the two former of these sub- 
stances having been already communicated to the Society, they are 
