714 



NATURE 



[January 27, 192 1 



Societies and Academies. 



, London. 

 Royal Society, January 20.— Prof. C. S. Sherring- 

 ton, president, in the chair.— Sir Robert Hadfield, 

 S. R. Wllliamg, and I. S. Bowen : The magnetic 

 mechanical analysis of manganese steel. Tests were 

 made on six rods quenched in water, when they are 

 in the non-magnetic condition, and three were after- 

 wards annealed, which rendered them magnetic. The 

 changes in length of the rods when subjected to mag- 

 netic fields were determined (Joule effect). In the 

 case of the rods in the magnetic condition the change 

 was an increment for all field strengths. No change 

 irl length could be detected for the non-magnetic 

 specimens. The effect on the intensity of magnetisation 

 when subjected to longitudinal stress (Villari effect) was 

 investigated. An absolute method of measuring the in- 

 tensity of magnetisation when comparatively small 

 was adopted, and for all field strengths the application 

 of tensile stress increased the intensity of magnetisa- 

 tion of the magnetic specimens. The non-magnetic 

 rods showed no change in intensity of magnetisation 

 by being stretched. They showed an intensity of 

 magnetisation about t/36th of that of the specitnens 

 ;n the magnetic condition, due entirely to oxidation 

 of the skin of the rods.— Dr. W. S. Tucker and E. T. 

 Pari* : A selective hot-wire microphone. The instru- 

 ment consists of an electrically heated grid of fine 

 platinum wire placed in the neck of a Helmholtz 

 resonator. The effect of a sound having the same 

 frequency as that natural to the resonator itself is to 

 produce an oscillatory motion of the air in the neck 

 of the resonator, which in turn causes changes in 

 resistance of the platinum-wire grid. The total resist- 

 ance change comprises a steady fall in resistance 

 due to an average cooling of the "grid, and a periodic 

 change due to the to-and-fro motion of the air. Two 

 methods of using the microphone are described : 

 fi) A bridge method, and (2) an amplifier method. 

 Curves are given showing the sharpness of resonance 

 as measured by the bridge method. Results of experi- 

 ments on cooling the grid by low-velocitv air-currents 

 are described. The principal resistance changes to 

 be expected when the grid is cooled bv an oscillatory 

 air-current are : (i) A steady drop due to an average 

 cooling; (2) a periodic resistance change of the same 

 frequency as that of the sound; and (3) a periodic 

 resistance change of frequency tw^ce that of the 

 sound. Further deductions are that the steady change 

 of resistance is proportional to the intensity of the 

 sound, while the periodic resistance change in (2) is 

 proportional to the amplitude. — E. A. Milne and R. H, 

 Fowler : Siren harmonics and a pure-tone siren. The 

 ordinary siren can be regarded as a ooint source of 

 air of variable flux, the flux being proportional to the 

 area of the orifice exposed by the holes in the disc. 

 The relative intensities of the harmonics for a siren 

 with circular holes and a circular orifice are calculated, 

 and it is concluded that a fairly pure note should be 

 obtained from a siren of this type, in which the dis- 

 tance between the centres of adjacent holes is twice 

 the diameter of the holes. If the original is rectangular 

 in section, the holes can be so shaped that the area of 

 the orifice exposed varies exactly as the sine of the 

 displacement.— L. V. King : The design of diaphragms 

 capable of continuous tuning. Continuous tuning is 

 achieved by the application of air-pressure (or suc- 

 tion). The diaphragm is constructed from a single 

 piece of metal, and consists of a thick, undeformable, 

 central disc connected by a thin, cencentric, annular 

 portion to a heavy, circular rim fitted accurately on 

 a rigid mounting. The application of air-pressure 

 NO. 2674, VOL. 106] ' 



over, the interior of the diaphragm alters the tension 

 of the thin annular portion, so that the rigid central 

 portion vibrates about the static equilibrium position 

 with a different pitch. To realise sharp tuning and 

 high sensitivity, diaphragms of this type should be 

 made with almost optical precision in the form of 

 accurate solids of revolution. 



Royal Meteorological Society, January 19.— Mr. R. H. 

 Hooker, president, in the chair. — Mr. R. H. Hooker : 

 Presidential address : Forecasting the crops from the 

 weather. Mr. Hooker remarked that forecasts of the 

 harvest fell into two main groups, viz. those which 

 predicted the recurrence of good and bad crops in 

 cycles, and those which computed the actual amount 

 by which the yield was improved or damaged by the 

 weather during or shortly before the growing period. 

 He outlined the evolution of the methods of ascer- 

 taining relationships between the weather at different 

 seasons of the year and the subsequent harvest. 

 Originally writers such as Gilbert and Lawes could 

 only examine the meteorological conditions in years 

 of exceptional abundance or scarcity. A great advance 

 was made when Sir Rawson Rawson and, later. Sir 

 Napier Shaw, from the study of an entire sequence 

 of crops and previous weather conditions, suggested 

 formulae from which the crop might be calculated, 

 while still wider possibilities were opened by the 

 methods of correlation. Mr. Hooker emphasised the 

 necessity of taking the past weather into account in 

 predicting the harvest, as it was abundantly clear, from 

 comparison with actual forecasts in India and else- 

 where, that the weather was responsible for develop- 

 ments in the plant which were not visible to an ob- 

 server surveying the young crops in the fields ; and, 

 although much work still remained to be done, the 

 time was ripe for using such statistics to confirm or 

 modify the results of direct observation of the grow- 

 ing plants. 



Rome. 

 Reale Accademia nazionale dei Lincei, November 7. — 

 Signor V. Volterra, vice-president, in the chair. — S. 

 Pincherle : Certain functional equations. — O. M. Cor- 

 bino : Electronic theory of electric conductivity in mag- 

 netic field. — F. Milloge'vich : Paternoite, a new mineral 

 from Calascibetta, Sicily. This is a borate of magnesia 

 containing chlorine, similar in appearance to stass- 

 furtite, and found in the saline deposits of Monte 

 Sambuco. — B. Longo : The " flowcless apple " {Pyrus 

 ape tola. Monch). This pjant only produces small 

 aborted pistilliferous flowers, and does not present 

 any trace of stamens. These flowers possess carpels 1 

 disposed in two planes, some of which contain more I 

 or less imperfect ovules. By fertilising with the - 

 pollen of other kinds of apples the author has obtained 

 actual seeds, which it is proposed to try growing. — 

 A. Denjoy : " Sur une classe d'ensembles parfaits 

 discontinus." — O. Onicescu : Spaces admitting in- 

 finitesimal translation along lines of zero length. — A. 

 dementi : A new hypothesis regarding the physio- 

 logical significance of protamines and histones in 

 nuclear exchanges.- — The president, Signor Volterra; 

 directed attention to the cost of printing scientific pub- 

 lications, and urged the necessity of State aid for this 

 purpose. The losses by death sustained by the 

 .Academy during the last session include Senators 

 Righi and Celoria and Profs. Cuboni, Beccari, Rajna, 

 and Giglioli. 



Melbourne. 

 Royal Society of Victoria, October 14.— Prof. A. J. 

 Ewart, president, in the chair.— D. K. Picken : A 

 generalisation of elementary geometry. The subject of 

 this paper was an outstanding defect of generality in 

 elementary geometry associated with the ambiguity 



