710 
Froceedings of the Royal Irish Academy. 
Ontarians. Any one driving through Connemara, or overlooking it from, 
the Twelve Pins (Bennabeola), can easily tell which hills are granitic 
gneiss and which are schist ; the same holds good in Canada, except that 
on account of the timber these rugged characters are in part blinded. 
The timber, to a novice, is at first puzzling ; but I suspect that to those 
used to the country it would not be so, as there are marked characters 
distinguishing the vegetation on the different strata. 
Log. cit., p. 630. — " These various rocks were eruptive — that is, 
that they originally formed portions of igneous materials that rose in a 
molten or plastic condition from below can hardly be doubted." 
Same page. — "Kowhere in the region to which I am referring has 
any trace of superficial eruption yet been detected, '^ot only so, but 
after the most careful search from Sutherland to Galway, not a vestige 
have we found of any unquestionable sedimentary materials. There are 
no conglomerates, no sandstones, no shales, not even any materials that 
might be supposed to represent them in a metamorphosed condition." 
To the statements in the two above extracts I cannot agree. 
The discoveries of Lapworth and others in l^orth-West Scotland 
are most important, and hereafter will materially assist in the correct 
mapping of all metamorphic rock areas, but unfortunately those working 
at the rocks are so blinded by the shearing discovery that they believe 
that shearing, and only shearing, is the main cause of metamorphic 
action. Those, however, who study metamorphism rationally, must be 
aware that, although shearing is a very important action, yet that it 
is only an adjunct to as great, if not greater, changes. 
The statements made in connexion with the "hornblende rocks" of 
Maculloch (diorite, syenite, &c., of other writers) illustrate the above. 
The normal hornblende rocks of Pennsylvania (as described by 
Lewis and Williams) — those of Ontario, Canada — of Wexford, of Galway, 
of Donegal, and elsewhere in Ireland — and of Sutherland, Scotland — 
graduate into nodular varieties, and the latter into schistose rocks, 
often nodular, the nodules having been called by the Scotchmen 
"eyes." 
The nodular varieties sometimes are found margining masses of the 
normal hornblende rock ; but more usually they occur at the ends of the 
long courses. The schistose varieties, called by me in previous writings 
hornhlendites,'^ if the nodular varieties are absent, margin the normal 
^ Dana makes the term hornblendite to include all the hornblendic rocks. After 
a correspondence on the subject I am led to believe that his use of the term is better 
than mine. It is, however, expedient to give my original definition of the term as 
used in my maps and writings. 
