( 18 ) 



7z-rays should be promoted to ol)Je('ti\e truth, our hypothesis would 

 receive a direct experimental support. 



At all events, the above has demonstrated that the principal mea- 

 surable phenomejia, noticed in the enzyme action are in harmony 

 with our hypothesis. 



Meteorology. — "()n, a t/ncnti/su-dfii/ peiiod in (hiihj means of 

 tke baiviiietrlc hehjld." By Dr. .1. P. van der Stok. 



i, A few years ago') Prof. A. Schuster investigated the problem, 

 how to detect the presence of a periodical oscillation, the amplitude 

 of which is small in comparison with large superposed tluctuations 

 which may be considered as fortuiloiis with respect to the purely 

 periodical motion. 



Starting from an aiialugy which may be seen between this question 

 and the problem of disturl)ances by \ibrations in the aether — a 

 problem treated by Lord RAVi,i',i(iii ') in J 880 — Prof. Schuster has 

 endeavoured to apply the theory of jtrobability to the determination 

 of the first couple of coeflicients of a Fourier series, and the method 

 he arrives at, aiul strongly advocates, is a[)plied to records of 

 magnetic declination observed at Greenwich during a period of 

 25 years. 



The choice of this material, in Prof. Schuster's opinion not favour- 

 able for the discovery of small etfects, is justitied by the remark 

 that "the only real pieces of evidence so tar (J 899) produced in 

 favour of a period a[)proximate]y coincident with that of solar 

 rotation were derivetl from magnetic declination and tiie occurrence 

 of thunderstorms.'" 



In this ami in an earlier |)aper ■') the author emphasizes that, in 

 inquiries of this kind, it is not at all sufKicient to come to some 

 result, but that it is necessary to apply a reliable criterion by 

 which a judgment may be formed about the value to be attached 

 to the result arrived at. 



His mathematical investigation, however, does not, lead to an out- 

 come which in every respect can be regarded as satisfactory, in so far 

 that a method of determining the mean and probable error of the 

 result from the series of observations themselves is not given and, 



1) Trans. Cambi. Phil. Soc. Vol. XVlll. 1809. 



2) Phil. Mag. Vul. X. 11, 1S8U. 



3) Tenestrial Magnetism Vol. Ill, 1896. 



