February 2, 1922] 



NATURE 



^Sl 



B. Topley : The influence of temperature on two alterna- 

 tive modes of decomf>osition of formic acid. Formic- 

 icid vapour in contact with glass surfaces between 

 and 300° C. decomposes mainly in the following 

 rays : — 



(a) H-COOH^COj+H, 

 {h) H.COOH=CO-hH,0. 



le two modes of decomposition proceed at approxi- 

 lately equal rates, but the critical energies calculated 

 rem the temperature-coeflicients of the respective 

 ilocity constants are so different that one reaction 

 lould predominate almost entirely unless a phase 

 sstriction is introduced. In this case molecules with 

 le necessary critical internal energy do not react 

 once unless they are in a certain phase. — C. V. 



iman : The molecular scattering of light in water 

 id the colour of the sea. 



Geological Society, January 4.— Dr. G. T. Prior, 

 Ice-president, in the chair. — W. D. Lang, L. F. Spath, 

 id VV. A. Richardson: Shales-with-beef, a sequence 

 the Lower Lias of the Dorset coast. Pt. i : Strati- 

 Jraphical, by W. D. Lang. The shales-with-beef lie 

 jtween Table Ledge below and the Birchi Bed above, 

 "and consist of an upper 30 ft. of brownish paper- 

 shales with selenite, "beef," and limestone-nodules 

 and lenticles; and a lower 40 ft. of bluish conchoidal 

 marls with indurated marl-beds, beef, and limestone- 

 nodules and lenticles. The main palaeontological divi- 

 sions were given. Pt. 2 : Notes on the ammonites, 

 by L. F. Spath. The genera of ammonites found in 

 the shales-with-beef are recorded, and remarks made 

 on their classification and phylogeny. Pt. 3 : Petro- 

 logical Notes, by W. A. Richardson. During sedi- 

 mentation, calcium carbonate gradually accumulated 

 in solution in the water-logged deposit, and a system 

 of limestones and calcareous nodules was precipitated 

 rhythmically during the initial stages of desiccation. 

 Later, veins of fibrous calcite were deposited at levels 

 of low pressure. On the final drying of the deposit 

 the remaining solutions of calcium carbonate were 

 ultimately dep>osited as a cementing material. 



Optical Society, January 12.— Mr. R. S. Whipple, 

 president, in the chair. — C. J. Peddle : The manufac- 

 ture of optical glass. The history of the manufacture 

 of optical glass can be divided into four epochs, 

 Guinand's discovery of the stirring process in 1796, 

 the work of Abbe and Schott about 1882, and the 

 development in England during the great war being 

 the outstanding features in this history. The method 

 of manufacture is practically the same at the present 

 time as in Guinand's day, any improvement being 

 one of degree rather than of kind. For successful pro- 

 duction of the various types the effects of composi- 

 tion upon density, refractive index, melting properties, 

 durability, freedom from colour, and devitrification 

 tendencies have to be studied upon a small scale and 

 the results translated into terms suitable for works 

 practice. — J. W. French : The Barr and Stroud loo-ft. 

 self-contained base range-finder. This range-finder 

 has a new type of triple field. It is carried upon a 

 mounting comprising two trucks running upon a roller 

 path of 50 ft. diameter, the trucks being connected by 

 a rigid horizontal framework. Upon the trucks are 

 carried cantilevers, from the ends of which are sus- 

 pended cradles having special bearings within which 

 the range-finder rests. Training is done by p>ower or 

 bv hand. During extensive tests the uncertainty of 

 observation at a range of -^1,000 metres did not exceed 

 20 metres. — T. Smith : The optical three-apertures 

 problem. In such an instrument as a submarine peri- 

 scope, where broad beams of light have to be trans- 

 mitted down a long tube from a wide field, the relation 



between the length and diameter of the tube and the 

 number of lenses is considered. Various types of 

 construction are indicated, together with the relative 

 advantages offered by them. 



Sheffield. 

 Society of Glass Technology, January 18. — Dr. M. VV. 



Travers, president, in the chair. — W. L. Baillie : An 

 examination and extension of Zulkowski's theory of 

 the relation between the composition and durability 

 of glass. Zulkowski's theory assumes that the 

 essential reactions involved in the founding of glass 

 are the formation of simple silicates of the alkalies 

 and alkaline earths which combine to form double 

 silicates. In these reactions the bases are regarded 

 as competing equally for the acids, and it is assumed 

 that all the materials of the batch enter completely 

 into reaction. If one type of base be molecularly in 

 excess, simple silicates remain in the glass, and are 

 regarded as the prime cause of instability. The dif- 

 ference between Zulkowski's original theory and that 

 now proposed is essentially in the different quantities 

 deduced for the number of molecules of simple sili- 

 cates present. The term "basic excess" is replaced 

 by a more complete function, for which the term 

 "reactivity coefficient " is suggested. Glasses of satis, 

 factory resistance have reactivity coefficients of under 

 three units. Negative values were generally asso- 

 ciated with the most stable glasseis, though very large 

 negative values are probably undesirable. — W. E. S. 

 Turner : A critical note on the methods of determining 

 the durability of glass. The method of stating the loss 

 in weight due to the attack of reagents is not a trust- 

 worthy check. It is better, where possible, to determine 

 either the amount of alkali liberated or the total 

 weight of matter extracted. With boiling re- 

 agents flasks gave different results from beakers, 

 and results differed according to the weight or 

 volume of the reagent they contained ; pieces 

 immersed gave results different from those obtained 

 where one surface only was in contact with the 

 reagent. Four modes of testing were discussed : — 

 (a) The static method with flasks and beakers, {h) the 

 use of slabs and discs immersed in the reagent, (c) the 

 autoclave test, and (d) a rapid method by grinding 

 glass to pass mesh 20-30. The autoclave test was 

 regarded as uncertain. For speed and convenience 

 test (d) was advocated. — Miss C. M. M. Muirhead 

 and W. E. S. Turner : The effect of magnesia on the 

 durability of glass. Lime and magnesia glasses 

 were compared. Resistance to attack by water 

 was determined from tests on glass crushed to mesh 

 20-30 and boiled for one hour. The amount of sodium 

 oxide set free was greater in the case of the lime 

 glasses than in the case of the magnesia glasses. The 

 results of tests on boiling discs in hydrochloric acid 

 for six hours showed that a glass containing small 

 amounts of magnesia was more resistant than the 

 corresponding lime glass, but the difference between 

 the resistance of the glasses is small when they 

 contain 8 or more per cent, of lime or magnesia. 

 Magnesia glasses are less resistant than lime glasses 

 to attack bv'both sodium carbonate and caustic soda 

 after boiling for three hours. 



Paris. 

 Academy of Sciences, January 16.— M. Emile Bertin 

 in the chair. — The president announced the death of 

 M. Ciamician. foreign associate.— F. E. Fournier : 

 The relations between the form of the hull of a shin, 

 the relative displacements of its satellite wave, its 

 aptitude for soeed, its most economical speed, and the 

 resistance of the water to its translation. — C. 

 Guichard : The 57 00 networks.— P. Montel : An exten- 



NO. 2727, VOL. 109] 



