49& 



NATURE 



[July io, 1913 



found that there are seven lines which are assoi iated 

 with the well-known spark line 4481-35, their wave- 

 lengths being 3104-91, 2661-00, 2449-68, 2329-68, 

 2253-94, 2202-75, and 2166-35. The eight lines, taken 

 ilteri ately, fall into two series having their common 

 limit at 49776 on the frequency scale. The series are 

 analogous to the two principal series of hydrogen 

 lines, which have recently been investigated by the 

 author. A. Fowler and W. H. Reynolds": Additional 

 triplets and other series lines in the spectrum of 

 magnesium. The paper gives particulars of eight new 

 triplets which have been photographed in the ultra- 

 violet spectrum of magnesium, and improved wave- 

 lengths for some of the lines previously recorded. 

 The Rydberg series of single lines has also been 

 extended, and four strong solar lines of previously 

 unknown origin have been identified with lines of 

 this series. Attention is also directed to a probable 

 second subordinate series of single lines. Formula? 

 representing the various series are given. — W. E. 

 Curtis : A new band spectrum associated with helium. 

 The paper desi ribes a new band spectrum observed 

 under certain conditions in vacuum tubes containing 

 helium and hydrogen. The experiments suggest that 

 the bands are due to helium, but until hydrogen can 

 be more completely eliminated their origin cannot be 

 regarded as definitely settled. — Sir W. de W. Abney 

 and Dr. YV. Watson : A case of abnormal trichromatic 

 colour vision due to a shift in the spectrum of the 

 green sensation curve. — Dr. E. F. Armstrong and 

 Prof. H. E. Armstrong : Studies on the processes 

 operative in solutions (XXX) and on enzyme action 

 (XX). The nature of enzvmes and of their action 

 as hydrolytic agents.— Prof. H. E. Armstrong and 

 H. W. Gosney : Studies of enzyme action. XXI. Lipase. 

 III. — Prof J. S. Macdonald :' Studies in the heat pro- 

 duction associated with muscular work. Preliminarv 

 communication.— Prof. F. Keeble, Dr. E. F. Armstrong, 

 and W. N. Jones: The formation of the Anthocyan 

 pigments of plants. Part vi. — T. Graham Brown : The 

 question of fractional activity ("All or None" pheno- 

 menon) in mammalian reflex phenomena. — J. H. 

 Andrew and Dr. A. Holt : The thermal effects produced 

 bv heating and cooling palladium in hydrogen. — Hon. 

 R. J. Strutt : A peculiar form of low potential dis- 

 charge in the highest vacua. — A. Mallock : Note on 

 copving machinery. — W. Wahl : The relation between 

 the crvstal-svmmetry of the simpler organic com- 

 pounds and their molecular constitution. Part ii. — 

 G. A. Shakespear : Experiments on the temperature 

 coefficient of a Kew collimator magnet. — W. Jevons : 

 Spectroscopic investigations in connection with the 

 active modification of nitrogen. III. : Spectra de- 

 veloped by the tetrachlorides of silicon and titanium. 

 — Lord Rayleigh : The passage of waves through fine 

 slits in thin opaque screens. — Prof. W. H. Bragg : 

 The reflection of X-rays by crystals. II. In a pre- 

 vious communication (April, 1913) it was shown that 

 the wave-lengths of homogeneous pencils of X-rays 

 could be expressed accurately in terms of the space 

 relations of a crystal. The formula X = 2dsin0 con- 

 nected the wave-length X with 0, the glancing angle 

 at which the pencil was reflected in the crystal face, 

 and d the distance between parallel reflecting planes. 

 The angle 6 could be determined with accuracy, but 

 want of exact knowledge of crystal structure threw 

 difficulties in the way of a complete evaluation of 

 wave-length. W. L. Bragg, using two independent 

 methods of research (those of the Laue diagram, and 

 of reflection in the crystal face), has shown that in 

 all probability the value of d is 2-81 x io -8 cm. From 

 this it follows that the wave-length of the " B peak " 

 is i-ioxio -8 . Characteristic radiations having wave- 

 lengths 1-25 x io- 8 and i-66xio -8 are emitted by 

 bulbs having antikathodes of tungsten and nickel 



NO. 228o, VOL. 91] 



respectively. So far as it has been found possible 

 measure the absorption coefficients, they belong 

 rays which are characteristic of the antikatho 

 metals, and the quantum energy — Planck's constai 

 multiplied bv frequency— agrees well with the energ\ 

 of the kathode ray which, according to Whiddington, 

 is required to excite the X-ray, or which the X-ray 

 can excite. — W. L. Bragg : The structure of some 

 crystals as indicated by their diffraction of X-rays. 

 An analysis of the Laue diagram of sylvine (KC1) 

 shows that the diffracting centres are arranged on a 

 space-lattice of the simplest cubical form. The dia- 

 grams of potassium iodide and bromide show that the 

 diffracting centres are arranged on a lattice the 

 element of which is the face-centred cube. Sodium 

 chloride is an intermediate case. From this and other 

 features of the diagrams, it is concluded that in all 

 these crystals the atoms of metal and halide are 

 arranged in a simple cubic lattice, rows parallel to 

 the axes containing alternate atoms of either kind. 

 In svlvini the equal weights of the atoms render 

 them" ee-.rtllv efficient as centres; in KBr and Ki the 

 heavy halogen atoms alone act, and so the pattern is 

 characteristic of the face-centred cube lattice. The 

 diagrams of other crystals are discussed in reference 

 to these conclusions; By means of the X-ray spectro- 

 meter, described in a previous paper, the dimensions 

 of these lattices can be accurately compared; and tin- 

 relative magnitudes of the different orders of spectra 

 reflected from any face, and from different crystals, 

 yield information which confirms the above conclu- 

 sions. It also appears that the weight associated with 

 each point of the lattice is proportional to the mole- 

 cular weight of the substance. These conclusions 

 yield the necessarv information for the accurate cal- 

 culation of the wave-length of the X-ray. — Leonard 

 Hill, J. M. McQueen, and W. W. Ingram: The 

 resonance of the tissues as a factor in the transmission 

 of the pulse and in blood pressure. — G. F. Davidson : 

 ExDeriments on the flow of viscous fluids through 

 orifices. 



Linnean Society, June 19. — Prof. E. B. Poulton, 

 president, in the chair. — E. G. Baker : African species 

 of the genus Crotalaria. Short descriptions are given 

 of the 309 species known to the writer as occurring- 

 in Africa. These are arranged in the following 

 groups: — Simplicifoliae, 39; Sphaerocarpae, 65; 

 Chrysocalycinae, 7; Farctae, 5; Spinosae, 3; Eucrota- 

 laria, subdivision Grandiflorae, 29; subdivision Medio- 

 criflorae, 61; subdivision Pariflorae, 49; subdivision 

 Oliganthae, 33 ; subdivision Stipulosae, iS. The genus 

 Crotalaria i- allied to Lotononis, and it is generally 

 easily distinguishable by the rostrate carina. — Dr. 

 W. T. Caiman : Aphareocaris, nom. nov. (Aphareus, 

 Paulson), a genus of the Crustacean family Serges- 

 tidae. — Dr. Agnes Arber : An anatomical study of the 

 cone-genus Lepidostrobus. — G. H. Wailes : Fresh- 

 water Rhizopoda from North and South America. 

 During- the year 1912 gatherings from the States of 

 Ne'w York, New Jersey, and Virginia provided re- 

 cords of twenty-four species and varieties of Rhizo- 

 poda, in addition to those enumerated in the paper 

 read before the society in April, 191 1. A number of 

 gatherings received from Mr. James Murray and col- 

 lected by him from various places on the east and 

 west 1 oasts of South America were examined, and 

 provided records of seventv-five species and varieties 

 of Rhizopoda, including three now described for the 

 first time. — C. Bucknall : A revision of the genus 

 Svmphytum. — S. Kemp : Pelagic Crustacea Decapoda 

 of the Percy Sladen Expedition in H.M.S. Sealark. 



Paris. 

 Academy of Sciences, June 30.— M. P. Appell in the 

 chair.— Paul Sabatier and M. Murat : The preparation 



