Abstract
LONDON Optical Society, June 9.—R. A. Houstoun: A new trichromatic colorimeter. The instrument is on a new principle, the intensity of the comparison field being altered by an iris diaphragm, and the colour by moving a magenta-yellow and a blue-magenta filter relatively to one another.—T. Y. Baker: The parallel plate micrometer. A plate of parallel glass placed in the convergent beam of a reading microscope is a useful means of obtaining the?fine-reading? of a divided circle. The fine-reading scale is uniform if its length is proportional to the tangent of the angle through which the plate is tilted and if the refractive index of the glass is 1 60.—J. Adamson: A study of the cyclorotational powers of the eyes. An expression for the?false torsion? of the eye is derived in terms of the direction of its line of fixation, and is used in calculating the extent of the compensatory cyclo-rotational powers of the eyes.—T. Smith: The hiding power of diffusing media. From theoretical considerations an expression is constructed as a numerical measure of the power of a sheet of a diffusing medium to hide the brightness contrasts of a surface on which it is laid. The dependence of this factor on the transmission and reflection factors of the sheet is exhibited and the effect of varying the thickness of the sheet is discussed. A comparison is made of these theoretical results with published experimental observations. The properties of all sheets may be expressed in terms of two constants, of which one is the reflection factor for an infinitely thick sheet, and the other is a factor for converting sheet thicknesses to the proper numerical scale. Geological Society, June 22.?Jane Longsta± (n©e Donald): A revision of the British Carboniferous members of the family Loxonematidæ, with descriptions of new forms. Many Carboniferous species have been referred to the genus Loxonema (Phillips) which do not strictly belong to it. This is the case with Etheridge?s Catalogue, where 25 species are given. Some of them, however, belong to the family Loxonematidæ as defined by Koken, and are referable to several of the genera into which it has since been divided. These are Zygopleura Koken, Katosira Koken, Microptychis Longstaff, and Hemizyga Girty. Three new genera are suggested for other species. The genus Zygopleura Koken contains by far the largest number of the species? one of these, Z. rugifera (Phillips), exhibits a considerable amount of variation both in size and ornamentation. The nuclear whorls, also, accord more with that genus than with Pseudozygopleura Knight. Twenty-six species and several varieties are described, 13 of the former being new. Six had been previously noted by de Koninck as common to Belgium, and another is now recorded: namely, L. subconstricta de
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societies and Academies. Nature 130, 178–180 (1932). https://doi.org/10.1038/130178a0
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DOI: https://doi.org/10.1038/130178a0