192 



NATURE 



[December 8, 19 lo Q 



locally between the labour exchanges and the education 

 authority, so that no actual overlapping of work shall take 

 place, but each be helpful to the other. 



The annual prize distribution of the Sir John Cass 

 Technical Institute was held on Tuesday, November 29, 

 when Sir William Tilden distributed the priies and 

 delivered an address ; the chair was taken by Sir Owen 

 Roberts, chairman of the governing body. Sir William 

 Tilden, after contrasting the conditions available for 

 obtaining scientific instruction now, in such institutions as 

 that of the Sir John Cass, as compared with his own 

 student days, referred especially to the improved character 

 of the teaching, but pointed out that the responsibility for 

 gaining the full benefit of these advantages rested still, 

 as it did in former years, far more with the students than 

 with the teachers. Whilst the business of the teachers 

 was to be regarded as being concerned with the selection 

 of the subjects to be studied rather than their exposition, 

 the real responsibility for progress must always rest with 

 the student. The assimilation cf knowledge is the busi- 

 ness of the student, and the greatest inducement and 

 stimulus for such assimilation is the desire for knowledge, 

 a desire which is most advantageously associated with a 

 conviction of ignorance. Sir William Tilden further urged 

 the necessity of the thorough understanding of the sub- 

 jects taught at each stage of progress, and pointed out 

 that students should not look to their teachers for recipes 

 for doing things, but to their own efforts, as the means 

 of acquiring a full understanding of their work, and that 

 they should not omit becoming fully conversant with the 

 history and meaning of the expressions and words employed 

 in their studies. In conclusion, it was pointed out that 

 with every student there are times when the mind should 

 be allowed to relax a little from the pages of their text- 

 books, and that of the many forms of relaxation it was 

 most desirable that all young English men and women 

 should devote some attention and interest to the history 

 of their own country. The exceptional advantages of 

 London, and especially of the City of London, as a stimu- 

 lant to such study was particularly referred to, for there 

 is nothing more interesting, more absorbing, or more 

 enchanting than the study of the history of mankind, 

 especially that particular variety of mankind which is 

 represented by the Anglo-Saxon race. Sir William Tilden 

 subsequently opened the new chemistry laboratory which 

 has recently been equipped by the governors of the 

 institute. 



SOCIETIES AND ACADEMIES. 

 London. 

 Royal Society, November 24. — Sir Archibald Geikie, 

 K.C.B., president, followed by Mr. A. B. Kempe, vice- 

 president, in the chair. — -Sir Norman Lockyer : The 

 sequence of chemical forms in stellar spectra. — A. 

 Mallock : Influence of viscosity on the stability of 

 the flow of fluids. The effect of this paper is to 

 direct attention to an observation made by the 

 late Mr. W. Froude, F.R.S., with regard to an ex- 

 periment on fluid jets, and to its application in 

 explaining some of the phenomena presented by the flow 

 of viscous fluids. The experiment referred to was shown 

 by Froude at the British meeting of the British Associa- 

 tion in 1875, and one of the deductions drawn from it was 

 that in a viscous flow the character of the stream differed 

 according as to whether the flow was towards decreasing 

 or increasing pressure.— Horace Lamb : Atmospheric 

 oscillations. The paper treats of the free oscillations of 

 an atmosphere, the temperature being a function of the 

 altitude, and the adiabatic laws of expansion being 

 assumed. In particular, the case of a uniform temperature 

 gradient is discussed in some detail. The possible oscilla- 

 tions are of various types, of which the most important 

 is of the character of a longitudinal wave. The results 

 are simplest when the equilibrium state is one of con- 

 vective equilibrium, and the velocity of the longitudinal 

 wave is then equal to the Newtonian velocity of sound, 

 \/(gH), corresponding to the temperature of the lowest 

 stratum. The bearing of the results on Kelvin's theory of 

 the semi-diurnal barometric oscillation is examined, and it 

 appears that the existence of a free period of the earth's 

 atmosphere, of somewhat less than twelve mean solar 



NO. 2145, VOL. 85] 



hours, is highly probable. Other types of oscillation 

 depend for their frequency on the degree of stability of the 

 atmosphere, and may in circumstances be comparatively 

 slow. It is possible that these may account for some of 

 the minor fluctuations of the barometer. The paper 

 includes also an examination of the theory of waves at a 

 surface of discontinuity. — P. J. Kirkby : A theory of the 

 chemical action of the electric discharge in electrolytic 

 gas and other gases. The complicated results attending 

 the passage of an electric discharge through electrolytic 

 gas, described in previous papers, and in particular the 

 chemical effects observed in the positive columns of long 

 discharges, were explained by the theory that the chemical 

 action is due to molecular dissociation effected by the 

 collisions of gaseous ions constituting the current with 

 the molecules of the gas, the atoms of which are thus set 

 free to enter into new combinations. In this paper an 

 account is given of experiments designed to determine both 

 the number of molecules of water (w) formed by the 

 passage of the atomic charge through i cm. of the positive 

 columns of various discharges passed through electrolytic 

 gas (aH^-nOj), and also the electric force (Y) within these 

 columns, the results providing data for testing and develop- 

 ing the theory. The chemical effects of the positive column 

 are attributed to the motion of the electrons alone. The 

 number of atoms of oxygen set free bj' the collisions of an 

 electron moving through i cm. in electrolytic gas at p mm. 

 pressure under the electric force Y is of the form 

 cpe-tpl"^ , whtre c, h are certain constants. Hence, if an 

 atom of oxygen can unite directly with a molecule of 

 hydrogen, w is proportional to cpe-i^fV. All the experi- 

 mental results satisfy this condition within error-limits in 

 the particular form w[p = y-g e-^^'ipiy , and thus support 

 the above theory as well as the hypothesis that water- 

 vapour is formed by the collision of an atom of oxygen 

 with a molecule of hydrogen. This equation involves that 

 the energy of formation of an oxygen molecule is less 

 than, and probably nearly equal to, 6-Xio-'^ ergs; and 

 experiments of Berthelot upon the heat of transformation 

 of ozone into oxygen are shown to be in fair agreement. 

 An estimate, 7X10-'^ ergs, is also given for the energy 

 of formation of a molecule of water vapour. These experi- 

 ments also prove, independently of theory, that dissociated 

 atoms of oxygen are not charged electrically. Similar 

 experiments were made with the gaseous mixture CO 4- H,. 

 The chemical effects observed in the positive column repro- 

 duce the main features observed with electrolytic gas, and 

 are explainable by a similar theory. — G. W. Walker : An 

 electrostatic voltmeter for photographic recording of the 

 atmospheric potential. The paper describes some experi- 

 ments made at Eskdalemuir Observatory with the object 

 of obtaining a simple and efficient voltmeter for continuous 

 photographic registration of the electrical potential at a 

 fixed point in the atmosphere. Experience has shown that 

 occasionally the instrument would require to register up 

 to fully 1000 volts -(- or — . Satisfactory results have 

 been obtained by means of a Dolezalek electrometer. The 

 usual sensitiveness was greatly reduced by using a 

 phosphor-bronze suspension, while the needle was loaded 

 to prevent tilting. A fixed difference of potential is applied 

 between the quadrants by means of one or two standard 

 cadmium cells, while the potential to be measured is 

 applied to the needle. The needle can now carry iioo volts 

 with perfect safety and stability,, while the scale value on 

 the paper is constant to within a few per cent, over a 

 range from —900 to -(-900 volts. Trial has been made of 

 a voltmeter (made in the workshop) similar in general 

 design to the Dolezalek, but in which the fixed difference 

 of potential between the quadrants is provided by making 

 the quadrants alternately of copper and zinc soldered 

 together and not insulated. Uniformity of scale value 

 has been obtained from about —500 to +500 volts, but 

 for higher potentials only approximate uniformity was 

 secured. This defect arises from want of mechanical 

 perfection of the quadrants and needle, and should dis- 

 appear in an instrument made with the same accuracy as 

 the Dolezalek. At present, also, the damping of the needle 

 during very rapid changes of potential is insufficient 

 Reference is made to certain points in the manipulatior 

 of sulphur for insulating, which have been found essentia 

 to secure good results. — Dr. T. H. Havelock : Optica 

 dispersion : an analysis of its actual dependence upor 



