March 22. 1900] 



NATURE 



501 



rc'sunU of mean and extreme values for the twenty- five years 

 1873-98. (2) Chemical analyses of air and water in different 

 parts of Paris, and researches relating to the comparative value 

 of various disinfecting agents. (3) Micrographical investigations, 

 with a view to determining the amount and nature of organic 

 dust in open spaces and in dwelling houses. The work of each 

 section is under the superintendence of an eminent scientific 

 authority, and the control of the establishment is invested in a 

 permanent Committee appointed by the Municipal Council of 

 Paris. 



The earliest authentic record of bubonic plague has hitherto 

 been accepted as dated 300 B.C. Drs. F. Tidswell and J. A. 

 Dick have, however, recently brought evidence before the 

 Royal Society of New South Wales to show that the epidemic 

 of 1 141 B.C., described in the First Book of Samuel (chs. iv.-vi.), 

 was true bubonic plague. After the Philistines had captured 

 the Ark of the Covenant and taken it to Ashdod, severe illness 

 broke out among the people. "The hand of the Lord was 

 heavy upon them of Ashdod, and He destroyed them and smote 

 them with emerods." The Ark was afterwards taken to Ekron, 

 and here again we are told " There was a deadly destruction 

 throughout all the city . . . and the men that died not were 

 smitten with the emerods, and the cry of the city went up to 

 heaven." The word " emerod " has usually been taken to 

 mean haemorrhoids, but in the revised version of the Old 

 Testament it is stated to mean tumour or plague boil. The 

 epidemic in Philistia occurred at the time of the regular plague 

 season, and mice are mentioned in con nection with it, which 

 furnishes additional evidence that the epid emic was plague, for 

 a connection between the death of rats a nd plague at Bombay 

 and elsewhere has beei clearly established. Taking all the 

 facts into consideration, there appears to be contained in the 

 few chapters of I. Samuel an account of an epidemic of bubonic 

 plague that occurred more than three thousand years ago, or 

 more than eight hundred years previous to the hitherto accepted 

 historic record. 



Part IV. of the sixth revised edition of Foster's " Text- 

 Book of Physiology " has been published by Messrs. Macmillan 

 and Co., Ltd, It deals with the senses, under sight, hearing, 

 taste and smell, and cutaneous and some other sensations. Dr. 

 W. H. R. Rivers has assisted Sir Michael Foster in the revision 

 of these chapters, and his name appears upon the title-page with 

 that of the original author. 



In the Transactions of the Nova Scotian Institute of Science 

 has appeared a series of papers, by Prof. MacGregor and his 

 pupils, on the application of the ionic hypothesis to mixtures of 

 solutions of electrol)rtes. Vol. x. contains a paper by Mr. J. 

 Barnes treating of the viscosity of mixtures of solutions of 

 various salts of sodium, potassium and barium, in which it is 

 shown that general formulae developed by Prof. MacGregor hold 

 in this case also. Given data as to the viscosity and electrical 

 conductivity of the constituent solutions, the viscosity of dilute 

 solutions of the salts under consideration can be predicted by 

 the dissociation theory within the limits of experimental error. 



The additions to the Zoological Society's Gardens during the 

 past week include a Silver Pheasant {Euplocamus nycthe- 

 nierus, i ) from China, presented by the Rev. J. O. Couss- 

 maker; a Greater Black- backed Gull {Larus marinus), 

 European, presented by Mr. W. Baker ; two Starred Lizards 

 (Agama stellio) from Egypt, presented by Mr. Stanley S. Flower ; 

 a Green Lizard (Lacerta viridis), European, presented by Mr. 

 W. J. R. Elgy ; two Grey Struthideas (5"//'«/Ai'</tfa cinerea) from 

 Australia, a Bennett's Wallaby {Macro/>us bennetti) from Tas- 

 mania, deposited ; a Black-faced Ibis ( Theristicus catidatiis) 

 from South America, purchased. 



NO. 1586, VOL. 61] 



OUR astronom}cal column. 



Comet 1899 V.— Herr S. K. Winther, of Copenhagen, com- 

 municates an ephemeris of this comet to the Astronomische 

 Nachrichten (Bd. 152. No. 3930), from which the following is 

 abstracted : — 



Ephemeris for izh. Berlin Mean Time. 

 1900. R.A. DecL 



P T^ j_^A°-^«A^rR-A. 20h. 29m. 



B.D.-f46 2966 -^j3^^, _^ ^go 



New Variable in Cygnus.— In \.h& Astronomische Naeh- 

 richten (Bd. 152, No. 3629), Mr. A. Stanley Williams, of 

 Hove, draws attention to the variability of the star 



,5-3 ^'"Ic*-)- 



The variable was detected from photographs taken with a 

 Grubb portrait lens of 4-4 inches aperture. The brightness was^ 

 found to change from 9'i magnitude, on 1899 October 2, to 

 I0"0 magnitude, on 1900 February 11, 



Inspection of reproductions from photographs of the star 

 taken by Prof. Max Wolf confirms the variability. In a photo- 

 graph taken June i, 1891 {.Knowledge, 1891, p. 189), the esti- 

 mated magnitude of the star is lO"2, while on another taken 

 September 9 and 10, 1891 {Knowledge, 1891, p. 188), the esti- 

 mated magnitude is only 9 '6. Most of the observations, visual 

 and photographic, furnish an approximate period of 31-0 days. 



Escape of Gases from Planetary Atmospheres.— In 

 the Astrophysical Journal, vol. xi. pp. 36-43, January 1900,- 

 Mr. S. R. Cook, of the University of Nebraska, particularises 

 part of the investigation of Dr. G. Johnstone Stoney, who 

 omitted from his discussions the determination, by the kinetic 

 theory, of the number of molecules which would have a velocity 

 sufficient to enable them to escape from the earth or planet, 

 assuming retarding media to be absent. The present author, in 

 commencing this discussion, refers to this velocity as the 

 critical velocity of the gas. 



The dynamical constants are computed for four different 

 conditions, including those adopted by Dr. Stoney, Prof. Cleve- 

 land Abbe (from balloon ascensions at Paris and Berlin), and. 

 the recent theoretical conclusions of Ferrel. From the result, it 

 is concluded that under the most probable conditions there 

 would be practically no escape of the gases nitrogen, oxygen, 

 hydrogen and helium from either the earth or the major planets. 

 An atmosphere like that on the earth, however, would not 

 remain on the moon. Tables are given showing the computed 

 temperatures at which the above gases would possess the 

 critical velocity for dissipation at the outer limits of the 

 atmospheres of the various planets. 



New Mode of using the Concave Diffraction. 

 Grating. — In the current number of the Mem. Soc. degli Spet- 

 troscopisti Ital. vol. xxviii. pp. 241-244, Dr. G. B. Rizzo, of the 

 Physical Institute at Turin, gives a description of his successful 

 experiments dealing with the manipulation of a Rowland Con- 

 cave Grating in other than the usual manner. The spectroscope 

 is generally so arranged that the grating and eyepiece or photo- 

 graphic plate are at opposite ends of a rigid beam which keejJS 

 them at the constant distance of the radius of curvature of the 

 grating, the plate being placed tangential to the focal curve. 

 This gives for a small distance on either side of the axis a prac- 

 tically normal spectrum, and although not normal, the other 

 orders of spectra are all brought to focus on the same focaV 

 circle, having as diameter the radius of curvature of the grating,. 

 It is evident, then, that whatever order of spectrum is being 

 observed normally at the end of the beam, there will be another 

 image, of the same order, on the other side of the central image 

 (which has been symmetrically reflected from the grating with- 

 out diffraction or dispersion), the lines of which will be in focus 

 along a circle having a radius equal to half the grating's radiu.s 

 of curvature. This second spectrum Dr. Rizzo designates the 

 internal spectrum, and its position is defined by the condi- 

 tion that 



sin tf= - 2 sin i, 

 where d is the angle of diffraction, 

 and I ,, ,, ,, incidence, 

 reckoned from the centre of the grating. 



