238 
MAJOR-GENERAL SABINE ON THE DISTURBANCES OF THE 
maxima and minima taken in absolute time, with the category of westerly disturbances 
at the other station. To test this by experiment, it was desirable to select stations, in 
suitable localities, where trustworthy observations could be relied on, inasmuch as the 
experiment would be somewhat of a crucial nature. The Eussian stations on the eastern 
side of Siberia and at Pekin, where hourly observations of the declination had been 
made for some years, seemed the most favourably situated for supplying a station on 
the eastern side of the Europseo-Asiatic focus, whilst Kew might furnish a correspond- 
ing station on the western side, as soon as its photographic records should be sufficiently 
advanced. For the Asiatic station Pekin was selected in the first instance, although its 
latitude being about 12° south of Kew, might seem to render it a rather less eligible 
station of comparison than one of the eastern-Siberian stations ; but there was at that 
time an idea, originated by Sir Charles Trevelyan at the Treasury, that Pekin might 
become a station of a British magnetic observatory, and in that view it was desirable to 
know what had already been accomplished there. The first thing to be done was to 
ascertain by a careful scrutiny the degree of reliance to be placed on the observations, 
these having been made, under the Eussian superintendent of the Pekin Observatory, by 
Chinese observers ; and a decisive test was at once adopted. It consisted in rewriting 
in lunar hours the monthly Tables which record the observations taken at solar hours, 
and deriving from the Tables so rewritten the lunar-diurnal variation. If this very small 
variation be shown consistently in different years by the observations thus transposed 
from the original record, the observations are entitled to be regarded as good. The 
Pekin hourly observations, from 1852 to 1855 inclusive, as printed in the volumes of the 
‘Observatoire Physique Central de Eussie,’ having been thus tested, were found to be quite 
trustworthy. The lunar-diurnal variation derived from them in each of the four years is 
shown in Table CXX., p. cxiv of the second volume of the St. Helena Observations, having 
been included in that volume for reasons stated in page cxxxvi. The aggregate values 
of the easterly and of the westerly portions of the disturbance-diurnal variation at Pekin, 
as well as the ratios of disturbance at the several hours, are printed in Table CXVIII. 
(p. cxi) of the same volume. The corresponding results obtained by the Kew photo- 
grams between January 1858 and December 1862 are given in a paper in the Philo- 
sophical Transactions for 1863, Art. XII., Table II., and in the same paper (Philosophical 
Transactions, 1863, Art. XII., p. 282) the comparison is made of the Kew and Pekin 
disturbance-deflections, showing that the conical form and single maximum which 
characterize the easterly deflections at Kew, characterize the westerly deflections at Pekin 
at approximately the same hours of absolute time. 
In confirmation of this result a second comparison was made between the results at 
Kew and those obtained from the hourly observations at Nertschinsk in Eastern Siberia 
from 1851 to 1857, printed also in the ‘Annales de l’Observatoire Physique Central 
de Eussie.’ Nertschinsk is almost identically in the same latitude as Kew, whilst in 
longitude it scarcely differs from Pekin. Here also the observations, having been sub- 
mitted to the same test in respect of accuracy, were found to be equally trustworthy ; 
