The remarkable organs which are frequently associated with the Zamia gigas of Lindley and Hutton, and which have always been considered as in some way connected with the fructification of that plant, are the only fossils that can be referred to Cycadean fruits that have been hitherto observed in the Yorkshire Oolites, in which the remains of Cycadean leaves are so abundant. These organs have been made the subject of an elaborate memoir by Professor Williamson, presented to the Linnean Society some months since, and which it is to be hoped will soon appear in the Transactions of that Society. He has brought together so many observations, made during a life-acquaintance with these beds, that he has been able to re-construct, with every appearance of truth on his side, a singular genus, containing two well-marked species, and forming a new tribe of Cycadeœ very different from any living form.

Although the geology of the Midland Counties has been considerably elucidated, still there appear to be some points connected with the position and nomenclature of the Lower Oolites which require re-examination.

The Skiddaw Slates, or Lowest Silurian Rocks of the Lake-district, are succeeded upwards by a great series of ashes with interbedded traps and porphyries, to which the name of “Green Slates and Porphyries” has been applied, and it has always been believed that the relations between the two were those of perfect conformity. As early, however, as the year 1867 I was led, from certain phenomena which I had observed, to express the opinion that “whether the Green Slates are really conformable with the Skiddaw Slates is a question which admits of doubt, though data are wanting to arrive at a definite conclusion.” (Geology of Cumberland and Westmoreland, p. 33.) In the beginning of November, 1868, I discovered what seemed to be a marked want of conformity between the Skiddaw Slates and the Green Slates, the localities where this occurred being the eastern side of the mouth of the vale of St. John, the west side of Derwentwater (near Lowdore), and the mouth of Borrowdale. As these phenomena had not been previously noticed by any former observer, and as they appeared to me to be of considerable importance, I have made a systematic investigation of the subject, and have arrived at the following results.

Denudation has been divided into only two kinds — viz., Subœnal and Marine; nevertheless, naturally there seem to be three marked denuding forces—I. Subœrial or Atmospheric; II. Marine; and, III. Glacial.1

As several papers by Mr. David Forbes and Mr. Sorby have probably by this time induced a few Geologists to turn their attention to the importance of a microscopical examination of rocks and minerals, it may interest some of your readers to know that the application of this method of research has just lead to a rather interesting discovery.

The Unconformity between the Green and Skiddaw Slates, which I pointed out in the last number of the Geological Magazine, (see p. 56) as exhibited between Grange in Borrowdale and Dale Head will, I think, explain satisfactorily the Geology of Derwentwater