A grant from the Government Fund enabled me to visit Iceland 1881, with a view of studying its interbasaltic flora. I explored considerable part of the island and visited every locality that I could reach where lignite had been met with. I did not take notes of some of the localities where my visits were hurried; but the conclusion I invariably arrived at was, that the sedimentary deposits in which vegetable remains are found, are situated among the glassy rhyolitic flows above the columnar series of basalt. The rhyolites are usually pale in colour, and with banded structure, but are sometimes black pitchstone or obsidian. They cap the loftiest mountains of the district west of Akreyri, and extend at least to Baula, a mountain in the same latitude as Snaefell, and possibly beyond this. They also occur on the east coast, though I did not reach any of them in that part of Iceland, which I only visited from the Danish mail-boat, which calls in many of the fiords. I did not pay particular attention to their thickness, but at Sandafell I measured 30 feet of white, pink, ivory-coloured, and black glassy lavas. The thickness is, I believe, sometimes greater than this, and they are interrupted and overlain by smaller flows of basalt. The horizon is, however certainly continuous, and marks a very definite stage or phase in the great series of Tertiary eruptions which extended from Ireland to Iceland in Eocene times. I cannot yet present data to show