Further proof is to be found in the facts that deep narrow fjords exist only on the east, north, and northwest coasts, where this older formation prevails, and not on the south and west, where the island is built up to a greater extent by the igneous rock which has coursed between the masses of the miocene formation -the ice-clad Joldar lying inland to the south and west of the elevated plateau of the Sprengisandr and Oddcfahraun. The way in which the fjord inlets radiate is convincing proof that they have been mostly hollowed out by glacial action; and in the north-west peninsula the glaciers are still doing their work, though perhaps not so vigorously as of yore, the glaciers being of less extent. Save on the north coast -where we find four, whose beds and continuous valleys lie between detached masses of the older formation, the fjords nowhere have deep continuous valleys that penetrate inland beyond the more elevated coastal region; and the river valleys, even those of the Skjdlfandafjot and JoJcidsd, rivers which intersect the island northward from the very base of the Vatna Jokidl, are of no great depth upon the plateau, but abruptly deepen as the coast is approached, the two rivers named each falling nearly a thousand feet in a few miles.
While upon the subject of the strata underlying the plateau bared in these long waterworn river beds, I will digress to briefly call attention to the way in which the geological student at the very commencement of his career is puzzled by the present classification of rocks,* by asking: In the face of the vast stratified formations of igneous rocks that have issued, and been deposited, subaerially, found all over the globe, is it not about time that such an absurd dogma as the one embraced in the following paragraphs was erased from works on geology ?
' There are thus in the crust of the globe only two great categories of rocks-the aqueous or stratified, and the igneous or unstratified; the former produced through and by the agency of water, the latter through and by the agency of fire.' ' Here, then, as we cannot regard nature acting in time past otherwise than at present, we are entitled to infer that all (!) rocks in the earth's crust occurring in layers have been formed through and by the agency of water.' The above are from ' Geology for General Readers," and I can only observe that it is a matter for regret that the author did not devote iess time to theoretical indoor study of the science of geology, and more to practical outdoor study in such lands as Iceland. The geological dogma that all stratified rocks are of subaqueous deposition has proved an incubus that previous writers when describing the geology of Iceland have not been able to shake off, not even Burton, for he guards his statements by the following footnote :-' The word " trap " will be used in these pages to denote the lavas ejected by submarine volcanoes/
* The term ' trap rock' is also very confusing. Dana applies the name to a ' dark greenish or brownish-black rock, heavy and tough. Specific gravity 2 8 - 3'2,' while Page says, ' Ti'ap-rock (so called from the step-like aspect it gives to hills composed of it) is a name which includes a great variety of igneous rocks, the general characteristics of which are easily (?) recognised in the field. Basalt and greenstone may be included under the term trap, but the name is generally applied to the looser and less crystallised masses, known as trap-tuff, wacko, amygdaloid, etc.'
To judge by the existing coastal formation of Iceland, the masses of the miocene plateau left standing subsequently to the disturbances of the glacial epoch were detached by arms of the sea as the Farces are to day, or what is perhaps more likely were separated by the arms of a vast glacier occupying the space now the interior of the island, which stretching seaward through rifts in and the gaps between the mountain masses, deepened and widened them into the fjord inlets of this remarkably indented island. Amidst the complex of mountainous isles left standing, existed a vast volcanic outlet that has remained active until this very hour; belching forth its fiery floods of molten rock to be deposited in the form of conglomerates and tuffs when they issued subaque-ously or subglacially, and later on, subasrially, in the form of the vast sheets of lava composing the more superficial strata of the inland plateau. Not only in the large space inclosed by the fragments of the miocene plateau was the molten rock so deposited, but coursing between the rifts and gaps a certain quantity was left behind, the sea and ice thereby being gradually ousted, and the detached masses connected by lower lying tracts into one island, with an exceedingly irregular coastal outline, and thus was the foundation laid of the Iceland of to-day.
There is reason to believe that the sea-level over the northern hemisphere varied considerably towards the close of the glacial epoch, and likewise during the early ages of the post-tertiary period, at times being far higher than at others. This would account for the tuff-strata found alternating with the lava ; as it is not very speculative to imagine that those portions of Iceland, including the interior, lowlying at that time would be flooded ; the volcanic vent converted for a period into a submarine volcano, and the molten rock that issued at such times be deposited in the form of tuffs and conglomerates. In the course of ages the whole of the spaces between the fragments of the miocene plateau were gradually upbuilded above the encroachment of the sea ; the currents and tides carrying away the greater part of the disintegrated igneous rock that found its way be}rond the outlying miocene bulwarks that now form a considerable part of the coastal region ; the climate became more temperate, no glaciers being found at a lesser altitude than 2,500 feet, and the later discharges of molten rock were deposited unchanged, save by congelation, in the form of the basaltic and other lava-strata that lie uppermost in the posttertiary plateau forming the greater part of the interior.