An electronically tuneable inductance with extended frequency range
The extension of the usable frequency range of an electronically tuneable inductance circuit is investigated. By means of numerical and analytical studies, the transistor-internal reverse transfer capacitance can be identified as a frequency-limiting element, which must be minimised. This is achieved by circuitry-wise compensation of the capacitive effect by introducing an additional inductance. The concept is verified through measurements of the practical implementation and shows an extension of the frequency range by two octaves throughout the VHF range, which proves beneficial for applications such as broadband matched and tuneable transmission lines, amplifier circuits, oscillators, or filters.
Experimental proof-of-principle of a passive, nearly reciprocal, transistor-based tuneable RF inductance
An innovative approach for tuneable reactances using the example of electronic inductances is introduced and the operation principle affirmed by measurement. Hitherto solutions for variable inductances often lack applicability in serial paths or do not exhibit passive behaviour. The presented circuit shows, even though transistor-based, a passive and reciprocal tuneable inductive behaviour at its terminals over a broad range of biasing conditions and frequencies. Thereby it accommodates more degrees-of-freedom in circuit design and possibilities for interesting applications, e.g., in integrated circuit design for a multitude of relevant applications in sensing and mobile communications. A test board was implemented and measured, confirming the principle-of-operation in agreement with numerical simulations, demonstrating a transistor-based, passive, tuneable, nearly reciprocal inductance over a frequency range larger than a decade.
THE GEOLOGICAL SURVEY IN YORKSHIRE
( Presidential Address delivered at Sheffield , 14 th December, 1957).

I. General History For some years after its institution in 1835 the Geological Survey was preoccupied with the south-western parts of Britain, and it was almost mid-century before the work of “making the geological map” was extended northwards to the borders of Yorkshire. Already several one-inch maps had been completed and were issued, hand-coloured, on what later became known as the “Old-Series” grid, and in 1846 De la Beche published his first volume of Memoirs of the Geological Survey. We find the name of Warington W. Smyth on a detailed section, dated 1845, of the first Woodhead Tunnel which lies partly in Yorkshire. And at about the same time William Smith’s nephew, John Phillips, was spending some eight years of his life on the staff of the Geological Survey, bringing to publication in 1852 the first official map to cover a part of Yorkshire—the original edition of the Old-Series sheet 81 NE., mainly covering the High Peak of Derbyshire but including, on its east side, small parts of the Yorkshire Coalfield near Sheffield.

Once started, the survey of Yorkshire continued at such a pace that its completion was announced in 1882. A small band of field geologists of outstanding ability was responsible for this feat: W. W. Smyth, A. H. Green, C. le Neve Foster, Clifton Ward and J. R. Dakyns who, with John Phillips, brought the survey of the Sheffield area, Sheet 82 NW., to its publication in 1867; W …