June 13, 1918] 



NATURE 



299 



\alues of the absolute temperature in terms of 

 Bernoulli's numbers. The data required for testing 

 :he formula have been supplied in a recent paper bv 

 i.ewis and Gibson, who have given values for the 

 ■ ntropy of the elements under the condition of constant 

 volume, and also under constant pressure. These 

 values were deduced from observations on the specific 

 heat assuming the truth of the heat theorem of Nernst, 

 that the entropy of every actual substance in the pure 

 state is zero at the absolute zero of temperature. It 

 is found that the formula of Ratnowsky gives values 

 for the entropy of a solid in very close agreement 

 with those obtained by Lewis and Gibson. The hypo- 

 theses assumed in the theory of Ratnowsky are dis- 

 cussed, and the conclusion is drawn that these are 

 probably justified as bting^ at least approximately true. 

 — T. Smith : Tracing rays through an optical system. 



Cambridge. 



Philosophical Society, May 20.— Prof. Marr, president, 

 in the chair.— B. Sahni : The branching of the 

 zygopteridean leaf, and its relation to the probable 

 pinna-nature of Gyropteris sinuosa, Goeppert. (i) The 

 supposed quadriseriate "pinnae" of "forms like 

 Stauropteris and Metaclepsydropsis are Tertiary 

 raches, the vascular strands of the secondary raches 

 (pinna-trace-bar, Gordon) being completely embedded 

 in the cortex oi the primary rachis. All Zygopterideae, 

 therefore, have a single row of pinnae on each side of 

 the leaf. (2) This revives the suggestion that Gyro- 

 pteris sinuosa, Goepp., is a free secondary rachis of a 

 form like Metaclepsydropsis. (3) The genus Clepsy- 

 dropsis should include Ankyropteris, because (a) a 

 fossil described in 19 15 (Mrs. Osborn, Brit. Assoc. Rep., 

 p. 727) combines the leaf-trace of Clepsydropsis with 

 the stem of Ankyropteris, the leaf-trace in both aris- 

 ing as a closed ring; (b) in C. antiqua, Ung., also the 

 leaf-trace arose similarly, as shown by a section 

 figured by Bertrand (Progressus, 1912, Fig. 21, p. 228), 

 in which a row of small tracheides connecting the inner 

 cpds of the peripheral loops represents those lining 

 the ring before it became clepsvdroid by median con- 

 striction. — The structure of fmesipteris Vieillardi. 

 Dang. The most primitive (least reduced) of the Psilo- 

 tales. Specifically distinct from T. tannensis in 

 (i) erect terrestrial habit, (2) distinct vascular supply to 

 scale-leaves, (3) medullary xylem in lower part of 

 aerial stem. — Acmopyle, a monotypic New Caledonian 

 Podocarp. Indistinguishable from Podocarpus in 

 habit, vegetative anatomy, drupaceous seed, mega- 

 spore membrane, young embryo, male cone, stamen, 

 two-winged pollen, and probably male gametophvte. 

 Chief differences: — (i) Seed .nearly erect; (2) epiina- 

 tium nowhere free from integument, even partaking 

 in formation of micropyle ; (3) outer flesh with a con- 

 tinuous tracheal mantle covering the basal two-thirds 

 of the stone. 



Dublin. 



Royal Irish Academy, May 13.— The Most Rev. J. H. 

 Bernard, president, in the chair.— J. A. McClelland 

 and J. Enright : Some properties of large ions. The 

 paper deals mainly with the determination of certain 

 constants in connection with large ions. One con- 

 stant, for example, is measured, showing the rate 

 at which small ions are attached to uncharged nuclei 

 so as to form the large ions. The rates of re- 

 combination of larf*e ions and of large and small ions 

 are measured, and also the average charge on the 

 large ions. 



May 27. — The Most Rev. J. H. Bernard, president, 

 in the' chair. — H. C. Plummet : The symmetrical o|)tic-il 

 instrument. Schwarzschild has discussed the third- 

 order errors of a symmetrical optical instrument on 

 the basis of Hamilton's characteristic function. This 

 NO. 257,7, VOL. lOll 



treatment leads to the desired end by assuming the 

 results of the Gaussian first approximation. In the 

 present paper the order of development is reversed and 

 a self-contained theory is obtained. This has the 

 advantage of greater simplicity and directness, and 

 it also makes clearer the actual degree of approxima- 

 tion, which would concf-rn the development to a still 

 higher order if required. The conditions for this 

 further dev.elopment are indicated. The aberrations 

 for a mirror system are deduced directly from those 

 for a refracting system. 



Royal Dublin Society, May 28.— Prof. J. A. McClel- 

 land in the chair.— Dr. W. E. Adeney and H. G. 

 Becker : The rate of solution of atmospheric nitrogen 

 and oxygen by water. Part i. : The rate of solution 

 by thin films of water. In this communication the 

 authors deal with the question of the rate at which 

 atmospheric nitrogen and oxygen are dissolved by the 

 surface layer of a quiescent body of water, apart from 

 that of the rate at which the same gases after solution 

 pass downwards through the lower layers of the water. 

 ' A new method of studying the rate of solution of these 

 gases by water, when the latter is exposed to them in 

 I thin films, is described and discussed. The method is 

 shown to give accurate and important results. — Dr. 

 I G. H. Pethybridge and H. A. Lafferty -. A disease of 

 i flax seedlings caused by a species of Colletotrichum 

 I and transmitted by infected seed.. The disease 

 ! described was submitted as a. form of "yellowing," 

 I but has proved to be one of the " damping-off " type. 

 I The parasitic fungus is described as a new species 

 1 under the name of Colletotrichum linicolom. Dor- 

 1 mant mycelium is present within the epidermis of 

 I the seed-coat of affected seeds, and seedling infection 

 i occurs from this during or subsequent to germination. 

 Disinfection of the seed with formalin and with 

 hydrogen peroxide gave good results, but did not 

 entirely suppress the disease. Infected seed has been 

 found in samples coming from Japan, Russia, Hol- 

 land, Ireland, Canada, and the 'United States of 

 America. 



Paris. 



Academy of Sciences, May 27. — M. P. Painleve in 



the chair.— G. Bigourdan : ' The astronomical station 



of the College of Clermont (first period) and the 



astronomical expedition to Siam. History of work 



done at this station between 1652 and 1685, and an 



account of the astronomical expedition to Siam in 



1687.— H. Le Chatelier and B. Bogitch : Tne use of 



the Brinell ball for testing construction materials. 



I For cements and silica bricks the method is modified 



! bv introducing a thin sheet of foil between the ball 



i and the material under test, the impressions being 



I then measured on 'he foil. Preliminary experiments 



: with blocks of lead and copper proved that the use 



I of the foil did not modify the diameter of the im- 



I prints. Tests with cement, plaster, silica brick, and 



I clav brick showed that the variations from the mean 



i were much less than in the usual crushing test. The 



j fact was brought out that the opposite faces of the 



j same brick often show marked differences in h&rd- 



ness. — C. de la Vall(ie Poussin : The maximum of the 



I modulus of the differential of a trigonometrical ex- 



I pression of limited order and modulus.— M. Balland : 



Wheat substitutes in munition bread. Details of 



i results with seventeen substitutes for wheat in bread 



are given. — M. Brarhet was elected a correspondant 



' for the section of anatomy and zooIog\- in succession 



to the late .M. Francotte.— L Martinet : .Syntheses In 



■ the a-naphtliindol series.— Mme. Karen Bramson : The 



manufacture of paper pulp from dead leaves. The 



paper pulp required by France in an average year 



amounts to about one-tenth that obtainable from the 



: dead leaves produced. _ As by-products 1000 kilograms 



