ON MAGNETIC OBSERVATIONS. 173 
down and the mean curve deduced from all the six years which have been 
investigated is 04. They conclude that ‘it would seem possible, know- 
ing one set of values for any particular year—Greenwich or Kew—to 
determine the other set, correct to within four-tenths of a minute.’ This 
close agreement strongly supports the views of Dr. Wild, and at the same 
time makes it possible to deal practically with the observations from 
many different observatories, and to obtain trustworthy results. These 
results completely confirmed those of Mr. Whipple, who made a com- 
parison of the methods of Wild and Sabine with that in use at Greenwich 
for the years 1870-72 (see ‘ British Association Report’ 1886, p. 71), as 
to the nature of the difference between the diurnal variations at Green- 
wich and Kew as given by the two methods of reduction. The Astrono- 
mer Royal has not only undertaken to select the five quiet days of each 
month and communicate them to the other observatories as soon as pos- 
sible after the end of each year, but he has also offered to reduce the 
Greenwich results by Wild’s method as well as by that now in use at 
Greenwich. 
The following list of quiet days has been prepared by the Astronomer 
Royal from the Greenwich records as suitable for discussion in the year 
1889 :— 
January . : - F ‘ - 3 35, .Osl by 24,08 te 
February . : : . : . : 4, 10, 13, 22, 25. 
March 5 . 2 : r : : 3, 10, 19, 21, 24. 
April . F . : - : : 5, 11, 16, 17, 19. 
May . 3, 9, 16, 21, 25. 
June . 5, 8, 12, 24, 27. 
July . 4, 9, 15, 22, 26. 
August 3, 5, 14, 24, 30. 
September = : c : : 4, 7; 15, 20; 29. 
October . : ‘ ; : : . 4, 11, 16, 23, 27. 
November . F 5 . “ : ‘. 5, 18, 15, 19, 21. 
December . < é ‘ : ‘ 4,10, 18, 19, 25. 
The Committee of the Falmouth Observatory and the Rev. W. Sid- 
greayes of Stonyhurst have expressed their willingness to accept the 
same series of days for discussion, and M. Mascart of Paris and M. Mou- 
reaux of Parc St. Maur will also select and use for discussion the same 
typical days. Dr. Wild has published in the Bulletin of the Imperial 
Academy of Science of St. Petersburg a paper on the normal variation 
and the disturbances of the declination, in which he recommends the 
adoption of his method, and shows that during the last fifteen years there 
have been on an average seventy-two days per annum suitable for dis- 
cussion as undisturbed days. Dr. F. Schmidt of Gotha has discussed the 
daily variation of terrestrial magnetic force for Vienna for every month of 
the years 1879-88, and has represented them as numbers of a periodic series. 
In consequence of the expression of their opinion in their reports of 
last year, ‘ that the establishment of a Magnetic Observatory at the Cape 
of Good Hope would materially contribute to our knowledge of terrestrial 
magnetism,’ this Committee has received a letter from Mr. David Gill, 
the Director of the Royal Observatory, Cape of Good Hope, offering every 
facility in his power to forward the objects of the Committee. Mr. Gill 
reports that there is ample room for the establishment of the necessary 
buildings, and that he is prepared with hearty good-will to undertake the 
direction, administration, and control of the work, but that an additional 
observer will be required to carry out the magnetic work under his direction. 
