From no part of the world have we of late years derived more additions to the Geological Record than from North America. Besides important additions to the earliest pages of that record, the rich collections made by the United States Surveyors, both of fauna and flora, from the Cretaceous, Eocene, and Miocene deposits, have thrown much light upon the life history of the Earth; and it is even contended that they have bridged over the interval which, notwithstanding the Maestricht beds, the Pisolitic, and the Faxoe Limestones, still remains sharply marked between the Cretaceous and Tertiary formations of Europe so far as they have yet been examined.

Recent excavations for buildings on the east side of Nottingham have afforded opportunities for observing the true character and development of the conglomerate at the base of the Lower Keuper, which did not exist when this district was visited by the Government Geological Survey. The fact that no fair equivalent of the Muschelkalk of Germany has been met with in England lends an interest to the beds at the junction of the Lower Keuper and the Upper Bunter which they would probably not otherwise possess. Thus the Geological Survey paid special attention to the scanty exposures of this junction that happened to exist twenty years ago in this part. The best section to be seen at that time, near Nottingham, was in a lane leading from the Mansfield turnpike road, a mile north of the town, to the Mapperley Hills, and is thus described by Mr. Aveline in his memoir on the Nottingham district (Sheet 71, N.E.):—“Near the bottom of the lane there are beds of coarse sandstone [Upper Bunter] slightly consolidated, with pebbles of various coloured quartz, quartz-rock, and other sandstones. There is no good bedding visible in this conglomerate, and lying on it there are thin and regularly-bedded fine sandstones of a red colour. This is the bottom of the Lower Keuper beds, and the line between the two formations is well marked, there being an apparent unconformity. There is about twelve feet of this red sandstone, and above it three to four feet of soft red loam, then a thin bed of coarse light sandstone, above this a bed of sand and marl, with some small pebbles of quartz, then alternations of dark and light-brown soft sandstone of various thickness, and red marly shale, which pass up into the Upper Keuper red marly shale with thin beds of white sandstone.”

In a paper read on February 23rd, 1876, before the Geological Society of London, I endeavoured to prove that the peculiar laminated or fissile structure, common in certain igneous rocks, was due to contraction, like the associated ordinary joint-structures. In the discussion which followed, an objection was made to my having quoted certain phonolites from Auvergne, in support of my theory, because it was well known that the fissile structure in the typical phonolites of Hungary was due to change in mineral composition, and so the result of a banded structure in the rock. That this was not the case with those Auvergne phonolites, I had already convinced myself by examination, both in the field and with the microscope, and I had nowhere asserted that the only way in which rocks could become fissile was by the particular cause which I had advanced; for, although I only knew the Hungary rocks from hand-specimens, I was aware of a somewhat similar structure in certain British rocks. I thought I remembered also one or two cases in these where the fissile and the banded structure were co-existent and independent, but as the criticism came from a quarter not to be neglected, I determined to re-examine these cases. This I have done on occasion of short visits to Arran in the past and present year, during which I have obtained materials which will, I think, further illustrate this, and throw some light on other rock structures. The points, then, upon which I shall touch in the present paper are the relation (I.) of fissile and banded structures; (II.) of banded, spherulitic, and perlitic structures.

The day on which I arrived at Tomsk, which was the 6th of October, I bought a small tarantass, and next morning I started, with some who had been fellow-passengers on the steamer, en route for Irkutsk. There were four conveyances between three parties, one of them being used exclusively for baggage. As each of these always needed three horses, and sometimes four, we often had difficulties at the post-station, where the post-master seemed disinclined to allow such a sudden draft being made upon his stables. Luckily my friends were high officials, and travelling on Government service, and their wants had from necessity to be supplied. My carriage being included with the rest, I went along comfortably and without delay, which would most certainly have occurred had I been alone. Before we were fairly outside Tomsk we ascended what I had, when at a distance, mistaken for hills, but which now appeared to be only a scarp-like face of a plateau, and we were soon upon a dusty road bounded by a low plantation of birch. Now and then we plunged down and over a small water-course, our momentum always carrying us some distance up the other side. Everywhere the country appeared as if it were an alluvial expanse; but in the vicinity I think there must have been some beds of rock, because everywhere along the road stone was being used as a material to repair it. This was yellow, argillaceous, and somewhat slaty in its character, perhaps having come from some of the Coal-measures which I believe exist in the vicinity of Tomsk.