446 



NATURE 



[June 2, 192 1 



these currents a narrow strip of foil is used which is 

 placed perpendicular to the disc and to one side 

 of the hot region. When at a considerable perpen- 

 dicular distance from the disc, and when the gas 

 pressure is sufficiently low to eliminate convection 

 currents, the deflections of the strip of foil are always 

 away from the hot region. When, however, the strip 

 is placed very close to the disc its deflections over a 

 certain range of gas pressure are towards the hot 

 region. These facts are explained by the tendency 

 of the thermal transpiration currents to drag the strip 

 with them. The paper emphasises one of the essential 

 difl'erences between thermal transpiration currents and 

 convection currents, namely, that while the latter 

 clearly depend otj gravitation, the former do not. 



Cambridge. 

 Philosophical Society, May 2. — Prof. A. C. Seward, 

 president, in the chair. — E. K. Rideal : Active mole- 

 cules in physical and chemical reactions. The 

 chemical nature of evaporation is established by the 

 calculation of heats of reaction from spectral data 

 with the aid of the quantum theor}\ Evaporation is 

 regarded as a monomolecular chemical change; 

 equating- the rate of evaporation to the rate of con- 

 densation when equilibrium is attained, the unknown 

 integ-ration constants of the Clapevron-Clausius 

 equation, and thus the chemical constants of Nernst, 

 have been determined. The values obtained agree 

 closely with those experimentally derived. The energy 

 of activation is probably an average value represent- 

 ing the mean energy of activation of a gram-molecule 

 of reactant, and a formula from which it can be cal- 

 culated is given. The hypothesis receives support from 

 the fact that at the critical temperature the radiation 

 intensity is at a maximum for light of the particular 

 frequency with which the active molecules are in 

 equilibrium. Wien's law AmT = constant = 0-28986 is 

 shown to be a simple variant of Trouton's rule 

 L = KTc. The value of K as calculated from the 

 purely radiation-derived data of Wien is found to 

 be 9866. The latent heats of evaporation calculated 

 from Wien's law are found for non-associating liquids 

 to agree verv closelv with those derived from vapour- 

 pressure data. The equilibrium of the active mole- 

 cules with the radiation may be ascribed to resonance. 

 — Dr. Hartridge :(i) An experiment which favours the 

 resonance theory of hearing". When the phase of a 

 musical note is suddenly altered by n- the note fades 

 momentarily to silence, and returns a moment later 

 to its former intensity. (2) A criticism of Wrightson's 

 theory of hearing. A mathematical analysis is ad- 

 vanced to demonstrate the existence of the coinci- 

 dences required by the theory between the lengths of 

 the periodically repeated time-intervals in the separate 

 tones and those present when all the tones are sound- 

 ing together. They are found to be imaginary. (3) A 

 method of proiecting- interference bands. If a cellu- 

 loid replica difl'raction grating be mounted in optical 

 contact with a polished metal surface, and a beam 

 of approximately monochromatic light be projected 

 into it, the spectra produced are crossed by inter- 

 ference bands. (4) A method of projecting absorption 

 spectra. If a celluloid replica diffraction g-rating be 

 mounted on the hypotenuse of a right-angled glass 

 nrism, ^yith the rulings parallel to the apex, and a 

 beam of approximately parallel light be caused to 

 enter along the normal to the base, a spectrum of wide 

 dispersion and great intensity is produced. (5) The 

 shift of absorption bands with change of temperature. 

 The absorption bands of blood pigment in the visual 

 region of the spectrum have been observed at the tem- 

 perature of evaporation of liquid air and liquid nitrous 

 oxide by dr\-ing films of a solution of the pigment 

 NO. 2692, VOL. 107] 



in gelatine on glass slabs and then immersing them 

 in the cold liquids. It is found that such films retain 

 their transparency. The reversion spectroscof>e shows 

 that both o- and ^-bands are sharper at low tem- 

 peratures, and that they are displaced towards the 

 violet end of the spectrum approximately 41 A. ^ The 

 change in wave-length cannot be due to change in re- 

 fractive index of the solvent, because dissolving blood 

 pigment in glycerine instead of in water leaves the 

 band unchanged.— Dr. H. S. Carslaw : The cooling of 

 a solid sphere with a concentric core of a different 

 material. The method used is to study the contour 

 integrals over a certain standard path. Estimates of 

 the age of the earth founded upon the present surface 

 temperature gradient are discussed. — C. R. G. Cosens : 

 An alignment chart for thermodynamical problems.— 

 Dr. T. J. r'A. Bromwich : Symbolical methods in the 

 theory of conduction of heat.— C. V. Hanumanta Rao: 

 A property of focal conies and of bicircular 

 quartics. 



Dublin. 



Royal Dublin Society, April 26.— Dr. F. E. Hackett 

 in the chair. — J. Davidson : Biological studies of 

 A\>his rumicis.—Yi. G. Becker : A new principle in 

 blow-pipe construction. The essential features of a 

 quick-change blow-pipe to operate with air at con- 

 stant pressure, such as is supplied by a blower driven 

 by power, are discussed and the necessity for air-jets 

 of different bore for the different flames is em- 

 phasised. The tubular shape common to all hitherto 

 existing blow-pipes is shown to be unnecessarily 

 cumbersome, and is therefore abandoned. A form of 

 blow-pipe giving a great range of flames (including a 

 flat blow-pipe flame), each provided with an air-jet 

 of suitable size and allowing of instantaneous change 

 from one to the other, was described, and an actual 

 blow-pipe constructed on this principle was shown in 

 operation. 



Paris. 



Academy of Sciences, May 9. — M. Georges Lemoine 

 in the chair. — F. Widal, P. Abrami, and J. Hutinel : 



Comparative researches on the working of the liver 

 following surgical anaesthesia produced by chloroform, 

 ether, nitrous oxide, or novocaine. It has been shown 

 in previous communications that slight functional 

 alterations in the liver can be detected by simple leuco- 

 cyte counts, after absorption of a glass of milk. The 

 method has been applied to the study of the func- 

 tional derangements of the liver produced by anaes- 

 thetics. Chloroform, ether, and nitrous oxide pro- 

 duced derangements of function, chloroform acting 

 most powerfully. Injections of novocaine were with- 

 out effect on the liver.— M. Georges Urbain was elected 

 a member of the section of chemistry in succession 

 to the late M. Emile Bourquelot.— F. Vaney : The 

 polynomials of Laguerre.— A. Angelesco : A repre- 

 sentation of polynomials by integrals. — R. Birkeland : 

 The convergence of the developments which express 

 the roots of the general algebraic equation by a sum 

 of hvpergeometric functions of several variables. — 

 B. Gambler : Real non-unicursal algebraic curves with 

 constant torsion. — M. Idrac : Experimental studies on 

 hovering flight. In an earlier note the opinion was 

 expressed that wherever birds are hovering in 

 stationary flight thev are always in a zone where the 

 wind ha"s a vertical ascending component. Results 

 confirming this view are now given, and records of 

 the variations in temperature and pressure of the air 

 taken on apparatus carried by captive balloons are 

 reproduced. — J. Vallot : Study of the diffuse radiation 

 of the sky compared with the direct solar radiation. 

 The total diffuse radiation is considerable, and may 

 amount to one-third of the solar radiation. — A. Leduc : 

 A new equation of state for gases based on a know- 



