April i, 1922] 



NATURE 



43" 



the partial closure of the lower portion of the selecting 

 slit. — J. Guild : The photometry of optical instru- 

 ments. A portable surface-brightness photometer of 

 the polarisation type for the measurement of the 

 fraction of the incident light transmitted or reflected 

 by an optical instrument, and for the measurement of 

 the relative brightness of different parts of a field of 

 \iew was described. The instrument is a modified 

 Wanner optical pyrometer. — T. Smith : A projective 

 treatment of the submarine periscope. The optical 

 events occurring in a periscope may be illustrated by 

 homocentric projection. This affords a simple means 

 of finding the relative advantages of different arrange- 

 ments of the optical system. — A. J. Dalladay : Some 

 measurements of the stresses produced at the surfaces 

 of glass by grinding with loose abrasives. The 

 stresses at the surface of a piece of " greyed " glass 

 were measured and the relation is shown between the 

 size of grains of the abrasive used and the stresses 

 produced. 



Linnean Society, March i6. — Dr. A. Smith Wood- 

 ward, president, in the chair. — C. E. Salmon : (i) 

 Sagina Jilicanlis Jord. It differs from S. apetala by 

 its tapering sepals, and by their being appressed to 

 the ripe capsule ; from S. ciliata by being more- 

 glandular, sepals less acute, and shorter in proportion 

 to the ripe capsule. (2) Cerastium siihtetrandnim 

 Murbeck. Occurs in Orkney and in W. Sutherland. 

 It differs from C. tetrandrum by being both pentamer- 

 ous and tetrandrous ; the lower bracts are smaller 

 than the stem-leaves, sepal tips are pointed, and seeds 

 smaller. (3) Arum italiciim Mill. Found in S. and 

 S.W^ England, it differs from A. maculatum by the 

 jietioles being much longer in proportion to the blade,/ 

 spathes are longer compared with spadix, ovaries 

 more numerous, and the spadix is differently shaped 

 and larger. 



Aristotelian Society, March 20. — Prof. G. Dawes 

 Hicks in the chair. — R. F. A. Hoernle : Some byways 

 of the theory of knowledge. In the attempt to give 

 scientific precision to their language, some philo- 

 sophers have introduced into theory of knowledge a 

 distinction between first-hand knowledge and second- 

 hand knowledge (or knowledge mediated by symbols), 

 alongside of the current distinctions between " know- 

 ledge by acquaintance " and " knowledge by descrip- 

 tion," or " immediate acquaintance " and " thought." 

 Acquaintance and immediate experience are, in 

 current theory, commonly characterised by absence 

 of language and of analysis, whereas first-hand know- 

 ledge, e.g. a botanist engaged in research, may involve 

 any amount of analysis and symbols. Yet there will 

 be no divorce of description from acquaintance, or of 

 thought from immediate data, but the data will be 

 ordered and acquire significance, and their meaning 

 will come to the investigator as fulfilled and realised, 

 in a sense in which it cannot do so to one who merely 

 reads his account at second-hand. The choice of a 

 terminology is no mere matter of words, for it is a 

 choice of meanings, and therefore of the qualities and 

 relations which we affirm as " true " and " real " of 

 the object under discussion. Definition merely leaves 

 open the question whether anything bearing the 

 character defined exists. The suggestion was made 

 that a comparative and systematic study of philo- 

 sophical languages is much to be desired as a pre- 

 liminary to rational choice, and, in any case, as a 

 help to mutual understanding. 



Dublin. 



Royal Irish Academy, February 13. — Prof. Sydney 



Young, president, in the chair. — S. Young : The 



vapour pressures and boiling points of non-miscible 



and miscible liquids and the composition of the | 



NO. 2735, VOL. 109] 



vapours (distillates) from such heterogeneous and 

 homogeneous mixtures. The formation of azeotropic 

 mixtures of minimum and maximum boiling point 

 was explained, and the case of ternary azeotropic 

 mixtures was especially considered. A large number 

 of these mixtures have been discovered since 1902, 

 and by plotting the boiling points of known ternary 

 and binary mixtures against the boiling points of the 

 aliphatic alcohols it is possible to predict with some 

 confidence whether the alcohols not yet examined will 

 form binary azeotropic mixtures with benzene, normal 

 hexane, or toluene, or ternary mixtures with one of 

 these hydrocarbons and water. 



Manchester. 

 Literary and Philosophical Society, March 7. — Mr. 

 T. A. Coward, president, in the chair. — W. M. 

 Tattersall : The sound-producing mechanisms of 

 Crustacea. Some species of Crustacea from the 

 shallow waters and shores of East Africa and others 

 from Australia exhibit mechanisms for the production 

 of sound. Three main types of sound-producing 

 mechanism are found, (a) Popping Type : The sound 

 is produced by the rapid withdrawal of a tightly fitting 

 peg from a socket. (6) Fiddle and Bow Type. Rapid 

 motion of a sharp smooth ridge or a row of granules 

 across a row or series of rows of regularly arranged 

 granules or tubercles or a file-hke series of ridges or 

 vice-versa produces the sound, (c) Plectrum Type. 

 Two series of stiff, hollow spines are rubbed together. 

 The first type is found in the snapping shrimps 

 (Alpheus) characteristic of coral reefs ; the second 

 type in the spiny lobster of British coasts, some 

 shore crabs from tropical waters like Matuta, Platyo- 

 nichus, Pseudozius and the amphibious crabs, 

 Ocypoda and Uca ; and the third type only in certain 

 river crabs in Africa. The stridulating organs occur 

 in both sexes. The sound is probably a warning-note 

 to keep intruders from a burrow already occupied. 



Official Publications Received. 



D6partement van Landbouw, Nijverheid en Handel. " 'S Lands 

 Plantentuin " (" Jardin Botanlque de Buitenzorg "). Treubia. 

 Recuell de travaux zoologiques, hydrobiologiques et oc6ano- 

 graphlques. R6dig6 par Dr. W. M. Docters van Leeuwen, Dr. K. W. 

 Dammennan et Dr. A. L. J. Sunier. Vol. 2, Livraison 1, D6cembre. 

 Pp. 155. (Buitenzorg : Archipel Druckkerij.) 



The Indian Forest Records. Vol. 8, Part 3 : The Beehole Borer 

 of Teak : A Preliminary Note on the Ecology and Economic Status 

 of Duomitus ceramicus, Wlk. in Burma. (Lepidoptera, Cossidce.) By 

 C. F. C. Beeson. Pp. iii + 105 +3 diagrams. 3 rupees. Vol. 8, Part 

 4 : Notes on Artificial Regeneration in Bengal. By A. K. Glasson and 

 others. Pp. Hi +33 + 11 plates. 2 rupees. (Calcutta: Government 

 Printing Office.) 



Carnegie Institution of Washington. Year Book No. 20, 1921. 

 Pp. xxii+475. (Washington.) 



Records of the Botanical Survey of India. Vol. 8, No. 3 : Flora 

 Arabica. By Prof. E. Blatter. Part III : Campanulaceae-Ver- 

 benaceae. Pp. 11+283-365. 1.1 rupee. Vol. 9, No. 1 : A Survey of 

 the Flora of the Anaimalai Hills in the Coimbatore District, Madras 

 Presidency. By C. E. C. Fischer. Pp. ii+218+xxi. 4.4 rupees. 

 Vol. 9, No. 2 : EuphorbiaceiB Novae e Peninsula Malayana. By 

 A. T. Gage. Pp. 11+219-250. 8 annas. (Calcutta: Government 

 Printing Office.) 



Report of the Proceedings of the Fourth Entomological Meeting held 

 at Pusa on the 7th to 12th February 1921. Edited by T. Bainbridge 

 Fletcher. Pp. xii + 401. (Calcutta: Government Printing Office.) 

 7.8 rupees. 



Koninklijk Magnetisch en Meteorologisch Observatorium te Batavia. 

 Verhandelingen No. 8 : Het Klimaat van Nederlandsch-Indi5 (The 

 Climate of the Netherlands Indies). By Dr. C. Braak. Deel 1 (Vol. 1) : 

 Algemeene Hoofdstukken (General Chapters), Aflevering 2 (Part 2) ; 

 With English Summaries. Pp. ill +65-147 +50. (Batavia.) 



The Rockefeller Institute for Medical Research. Organization and 

 Equipment. Pp. 25. (New York.) 



Library of Congress. Report of the Librarian of Congress and 

 Report of the Superintendent of the Library Buildings and Grounds, 

 for the Fiscal Year ending June 30, 1921. Pp. 207. (Washington : 

 Government Printing Office.) 



Publikationer fra det Danske Meteorologiske Institut. Aarboger. 

 Isforholdene I de Arktiske Have (The State of the Ice in the Arctic 

 Seas) 1921. By Kapt. C. I. H. Speerschneider. Pp. 32+5 maps. 

 (Kjebenhavn : G. E. C. Gad.) 



