On the Buckling of Deep Beams. 1023 



not give conclusive evidence of the presence of ionization 

 below the normal ionizing voltage of helium. 



There is, of course, ample evidence from spectroscopic 

 observations * that when the pressure of the gas is consider- 

 able, ionization, which is presumably produced by cumulative 

 action, occurs below the normal ionizing voltage, but this 

 does not show, as Prof. Oompton implies in his recent paper, 

 that the results of the experiments we have criticized are 

 reliable. 



In regard to our criticism of Prof. Compton's original 

 contention that the neon which was present in the helium 

 used in his e;irlier experiments would be incapable of causing 

 the effects he obtained at different pressures, it must be 

 pointed out that the interesting new evidence of the purity 

 of the helium used in the later experiments does not affect 

 our objection to his original contention. 



CVII. On the Budding of Deep Beams. 

 To the Editors of the Philosophical Magazine. 

 Gentlemen, — 



IN connexion with the two papers on the Buckling of 

 Deep Beams published in your periodical (see Dr. J. 

 Prescott, xxxvi. p. 297 and xxxix. p. 194), I beg to communi- 

 cate the following : — 



The question of the buckling of beams can be regarded as 

 solved for a long time already. The first paper on this 

 subject was published in your periodical by A. Gr. M. 

 Michell, 1899, vol. xlviii. The same problem was investi- 

 gated with more details by Prof. L. Prandtl, 1899 [Munich 

 Dissert.). In both these papers, as also in the paper of 

 Dr. J. Prescott, the bending of the flanges of girders by 

 sideways buckling is neglected, and in consequence of 

 •that the results cannot be applied to the calculation of 

 I girders. 



The influence of the flexion of flanges of the girder was 

 studied by me, and the results were published in Russia, 

 1905 (Bulletins of the Polytechnical Institute, Petersburg). 



The translation of this paper in German can be found in 

 Zeitschr.f. Math. u. P//?/s., Bd. lviii. (1910). Other manner of 



* 0. W. Eichardson and C. B. Bazzoni, Phil. Mag. vol. xxxiv. p. 285 

 (1917) ; K. T. Cornpton, E. G. Lilly, and P. S. Olmstead, Phys. Rev. 

 vol. xvi. p. 282 (1920) ; A. C. Davies, Proc. Koy. Soc. A, vol. c. p. 599 

 (1922). 



