I wish in the present paper to draw attention to one aspect of the Whin Sill specially, viz. its aspect as an assimilater, and other interesting points connected with it I shall only mention incidentally, as they may arise during our investigation of this aspect.

In my first communication on the Carnivora I gave, at the commencement, a list of all the species said to have been found in on thethe “ Forest Bed,” and then at the end a corrected list. The same course will be followed in the present instance, so as to show at a glance, those species which have been removed and those which have been added to the list.

Diabase-porphyrite—from hill designated as a Trigonometrical Station 1½ mile N.N.E. from Pwllheli: the hill is quarried for road metal; a good hand-specimen is easily obtained; it has a dark-green ground with porphyritic felspars up to ¼ inch long of pale greenish colour; a little pyrites; very slight effervescence with acids.

Few spots on the face of the globe of the extent of Iceland could be mentioned where, within the same space, an equal number of volcanos could be found. In that island, too, many volcanic eruptions have occurred, which have been, perhaps, of greater magnitude than any others recorded as having taken place anywhere else on the earth. And yet the volcanos of Iceland are but imperfectly known, and, with the exception of two or three, not one of the rest has ever been scientifically examined. Hence the fact, that geological manuals so frequently contain most erroneous statements concerning this subject. A general uncertainty prevails as to how many volcanos have actually been in a state of eruption within historical times; dates are dealt with in a confused manner; and frequently mountains come to figure as volcanos which have never shown any signs of eruptive activity.