December 13, 1900] 



NATURE 



165 



temperature the results are more difficult; to interpret ; while 

 nitrogen maintains its nearly constant value for P.V., helium 

 decreases rapidly, then increases, and the same peculiarity is to 

 be remarked with the other gases, although they do not give 

 the product of P.V. coinciding with that calculable by assuming 

 that the increase of P.V. is proportional to the rise of absolute 

 temperature. 



These last experiments must be taken as merely preliminary ; 

 but they show that further research in this direction would be 

 productive of interesting results. 



The spectra of these gases have been accurately measured by 

 Mr. E. C. C. Baly, with a Rowland's grating ; the results of 

 his measurements will shortly be published. It may be 

 remarked, however, that the colour of a neon-tube is extremely 

 brilliant and of an orange- pink hue ; it resembles nothing so 

 much as a flame ; and it is characterised by a multitude of 

 intense orange and yellow lines ; that of krypton is pale violet ; 

 and that of xenon is sky-blue. The paper contains plates 

 showing the most brilliant lines of the visible spectrum. 



That the gases form a series in the periodic table, between 

 that of fluorine and that of sodium, is proved by three lines of 

 argument : — 



(1) The ratio between their specific heats at constant pressure 

 and constant volume is I '66. 



(2) If the densities be regarded as identical with the atomic 

 weights, as in the case with diatomic gases such as hydrogen, 

 oxygen and nitrogen, there is no place for these elements in 

 the periodic table. The group of elements which includes 

 them is : — 



(For arguments in favour of placing hydrogen at the head of 

 the fluorine group of elements, see Orme Masson, Cheni. News, 

 vol. Ixxiii. , 1896, p. 283). 



(3) These elements exhibit gradations in properties such as 

 refractive index, atomic volume, melting-point and boiling- 

 point, which find a fitting place on diagrams showing such 

 periodic relations. Some of these diagrams are reproduced in 

 the original paper. Thus the refractive equivalents are found 

 at the lower apices of the descending curves ; the atomic 

 volumes, on the ascending branches, in appropriate positions ; 

 and the melting- and boiling-points, like the refractivities, 

 occupy positions at the lower apices. 



Although, however, such regularity is to be noticed, similar 

 to that which is found with dther elements, we had entertained 

 hopes that the simple nature of the molecules of the inactive 

 gases might have thrown light on the puzzling incongruities of 

 the periodic table. That hope has been disappointed. We 

 have not been able to predict accurately any one of the 

 properties of one of these gases from a knowledge of those of 

 the others ; an approximate guess is all that can be made. The 

 conundrum of the periodic table has yet to be solved. 



ACTION OF TERRESTRIAL MAGNETISM ON 



THE RATES OF CHRONOMETERS. 

 T N the issue of the Comptes rendus of the Paris Academy of 

 ■•■ Sciences for November 26, vol. cxxxi., pp. 859-865, there 

 is an important communication by Prof. A. Cornu, dealing with 

 an experimental investigation .of the action of a terrestrial 

 magnetic field on the rate of a magnetised chronometer. 



The observations have been carried out on a pocket half- 

 chronometer, provided with anchor-escapement, compensated 

 balance and palladium spiral, whose rate had previously been 

 very satisfactory, but which had inadvertently become magnetised 

 by a large electro-magnet. The generally prevalent idea is that 

 a magnetised watch is quite untrustworthy until it has been 

 completely demagnetised, but the author's research has con- 

 vinced him that there is evidence of a regular law in the rate of 

 such an affected timepiece, and therefore it should be possible 



NO. 1624, VOL. 63] 



to neutrali.se the disturbance, either by tables of correction 

 formulae, or by suitably disposed compensators. 



The magnetisable parts are the pivots, anchor, spring, balance- 

 wheel and accessories to the escapement. In watches of 

 precision all direct contacts between steel parts are avoided by 

 the use of hard stone bearings, so that the mutual actions are 

 inductive effects. If, then, the watch be laid on a horizontal 

 table at a definite orientation, the only disturbing external force 

 capable of affecting its rate will be the terrestrial magnetic field. 

 To test this, provision was made for varying the orientation of 

 the balance by making the horizontal support movable about a 

 vertical axis, and then keeping the watch or clock for several 

 days successively in the four positions corresponding to the 

 hours XII, III, VI, IX, pointing respectively to the Magnetic 

 North. 



Systematic observations from 1898 June 20 to 1900 November 

 17, furnish a series of values for the variations in rate at the four 

 orientations, and the discussion of them has enabled Prof. Cornu 

 to show that they may be represented by a sinusoid. The 

 magnetic state of the watch remains sensibly constant ; the 

 semi-amplitude of the variations with the orientation was iO"37 

 sees., and the mean azimuth of the ascending node of the 

 sinusoid about 260° 21'. This result is especially interesting 

 and important in that this sinusoidal law is identical with that 

 obtaining when a watch having a balance wheel slightly out of 

 equilibrium is hung with its dial vertical and oriented to differ- 

 ent azimuths. That is, gravity also produces, if the mean 

 amplitude remains constant, a couple proportional to the vertical 

 projection of the eccentricity of the centre of gravity. Here a 

 series of observations of the rate of the same watch before it was 

 magnetised are given, taken during the period 1890 October 

 26-1891 January 25, showing the fulfilment of the sinusoid 

 law in this respect. 



It would thus appear that the condition discovered by Phillips 

 (Annaks des Mines, 6th series, vol. ix., p. 321, 1866) for elimin- 

 ating the disturbance due to gravitation may also be applied to 

 the compensation for magnetisation. 



As a crucial test of the truth of his deductions. Prof. Cornu 

 performed a substitution experiment in which the earth's mag- 

 netism was directly allowed for. In a piece of cork of exactly 

 the same form as the watch a cylindrical hole was cut in the 

 position corresponding to the balance wheel. In this was sup- 

 ported a small compass needle, and the whole supported on a 

 horizontal table. By means of a jointed arm a bar magnet was 

 held in such a position that the earth's magnetism was neutral- 

 ised, leaving the needle astatic. This done, the watch was 

 substituted for the cork, the orientation of the balance wheel 

 being the same as the small compass in the cork. This substi- 

 tution of cork model, getting astatic position by bar magnet, 

 and replacement of watch, was repeated for the four orientations, 

 and the daily rate carefully determined. It was found to be 

 sensibly constant in all positions. 



The paper concludes with the following summary : — 



( 1 ) Chronometers of precision are influenced by variations of 

 the magnetic field in which they are placed to an amount 

 depending on the degree of magnetisation of the balance wheel 

 and spring. 



(2) It is important to determine the magnetic moment of the 

 balance wheel, mounted or not on the spiral. 



(3) In observatories studying chronometer rates it is necessary 

 to regularly determine the comparative variations in four rect- 

 angular azimuths for calculating the formulae of correction. 



(4) In all cases it should be the endeavour to attain an ampli- 

 tude of 440° for the oscillations of the balance wheel, as 

 recommended by Phillips, to eliminate the action of the terrestrial 

 magnetic couples. 



(5) For precaution, in observatories as well as on board ship, 

 it would be well to envelop each chronometer with a thick box 

 of iron, so that the relative action of the terrestrial field may be 

 lessened. C. P. B. 



THE EFFECTS OF AN EARTHQUAKE ON 

 HUMAN BEINGS. 

 PAPTAIN BUTTON'S valuable memoir on the Charleston 

 earthquake of 1886 contains many accounts of the effects of 

 this great earthquake on human beings. Nowhere could they 

 be more vivid than in Charleston itself. " On every side," says 

 one witness, " were hurrying forms of men and women, bare- 

 headed, partially dressed, some almost nude [the earthquake 



