1030 REPORT—1885. 
apparently identical with the ‘ pipe-rock’ of north-western Scotland, has, like it, 
been compressed to such a degree that the vertical casts are flattened out and 
elongated in the direction of lamination to several times their original length. In 
the same sandstone quartz pebbles have been pulled out and flattened, while sericate 
has been largely developed along the cleavage planes. ‘The pressure can be shown 
to have been directed mainly from the south-east. 
2. The second locality is in the midst of the Laurentian area of Bucks County, 
and is known as Van Artsdalen’s Quarry. A mass of crystalline limestone is here 
mingled with an eruptive diorite in such manner as to show that it had actually 
flowed like an igneous rock and had caught up inclusions. The results of extreme 
metamorphism are exhibited in the development in the limestone of graphite, 
ekebergite, and other minerals. The chemical changes and interchange of elements 
which might result from a loosening of molecular combinations under extreme 
pressure and their subsequent ‘rezelation’ into new compounds were discussed as 
among the phenomena of mechanical metamorphism. 
3. As an American instance of the conversion of an intrusive diahase dyke 
into amphibolite schist, analogous to the case recently described by Teall, a long 
narrow belt of sphene-hearing amphibolite schist in the city of Philadelphia was 
adduced. This belt, with distinctive mineralogical characters, cuts across the 
metamorphic mica schists of the region unconformably, and is believed by the 
author to be a highly metamorphosed intrusive dyke of Lower Silurian age. The 
original augite or diallage has been completely converted into fibrous hornblende, 
and the influence of pressure is shown in the perfectly laminated character of the 
schist, in the close foldings produced, and in the minute structure of the rock. 
Some interesting details of the latter having been photographed, diagrams con- 
structed from these were exhibited. These showed that the rock was traversed 
by a parallel series of slips and crushings, and that about such lines of faulting and 
crushing there was a peculiar arrangement of the lines of hornblende crystals not 
very unlike the arrangement of iron filings about the poles of a magnet, such as 
could not be satisfactorily explained by any theory of aqueous deposition, but 
pointed to a lamination by pressure. 
5. On Slaty Cleavage and allied Rock Structures, with special reference to the 
Mechanical Theories of ther Origin. By Atrren Harker, M.A., 
F.G.S.—See Reports, p. 818. 
6. On Irish Metamorphic Rocks. By G. Henry Kinanan, MR.LA. 
This paper is an epitome of what is known as to the age of the Irish meta- 
morphic rocks. The author gives ten Irish localities in which the rocks litho- 
logically are more or less identical with the Laurentian rocks of America. Of each 
locality a short description is given, and where the age of the rocks is positively 
proved it is stated, while in the other cases the probable age is suggested. He also 
points out that while in some cases lithological characters are taken as a sure test 
of Laurentian age, in other cases they are ignored, by which means many rocks 
eminently lithologically similar to some of the Canadian rocks have been excluded 
from the so-called Irish Laurentians. 
7. On Rocks of Central Caithness. By Joun Gunn. 
The term ‘Central Caithness’ is intended to embrace most of the parish of . 
Halkirk and part of the parish of Watten. 
The upper part of the parish of Halkirk is covered by drift gravel, underlying 
peat. At Loch More flagstones are presented. Below the lake may be traced the 
banks of what was once a great river. At Dirlot the rocks are sandstone, granite, 
gneiss, gneissic conglomerate, and limestone. At Dalmore the right bank of the 
Thurso is composed of boulder clay, the left of grayel. Here is seen a chain of 
