172 REPORT—1890. 
corrected every day by a time signal sent from Tokio. Although the 
hearty thanks of the Society are due tu the Telegraph Bureau for the 
manner in which they have rendered assistance, I regret to report that 
although the observations have thrown some light on the distribution of 
seismic energy in North Japan, records which are of value in determining 
the velocity of earthquake transmission have not yet been obtained. 
One or two of the observations, which have extended over a period of 
two years, suggest that at least sometimes a given earthquake may be 
felt simultaneously over an area of considerable extent. This was the 
case with the disturbance of August 2, 1889, which was noted at several 
places about 100 miles apart at exactly the same time. 
At present we have reliable observations on the propagation of earth- 
waves varying between 200 and 6,000 meters per second, whilst at other 
times it appears as if a large area received an impulse in all its parts at 
the same moment. 
Siath Report of the Committee, consisting of Professor W. GryLLs 
Apams (Chairman and Secretary), Sir Witt1am Tuomson, Sir 
J. H. Lerroy, Professors G. H. Darwin, G. Curystan, and S. J. 
Perry, Mr. C. H. Carpmazt, Professor Scuuster, Professor RiickEr, 
Commander Cruak, the Astronomer Roya, Mr. Witu1am ELLs, 
Mr, W. Lanr Carpenter, and Mr. G. M. Warprir, appointed 
for the purpose of considering the best means of Comparing 
and Reducing Magnetic Observations. 
Aw attempt has been made during the year to organise and bring into 
form the recommendation of this Committee, made in their report of last 
year, that it would be desirable to publish annually the curves of the 
three magnetic elements for different Magnetic Observatories for certain 
selected days. 
This matter has been under the consideration of the Kew Committee 
of the Royal Society, and a Sub-Committee of that body has been appointed 
to take charge of it, the Sub-Committee consisting of Professor W. Grylls 
Adams, Professor Riicker, Commander Creak, with Mr. Whipple as their 
Secretary (all of whom are members of this Committee). 
It seemed of some importance to decide how many days in each month 
would be required in order to give accurately the mean diurnal range 
without requiring the elaborate measurements and methods in use at 
Greenwich, which would be impracticable in observatories where only a 
small staff is employed. : 
With this object it was proposed by Professor Riicker to employ the 
method proposed by Dr. Wild! to reduce the mean diurnal range of 
declination at Kew for two or three years previous to 1888, taking only 
five quiet days in each month. The years selected were 1883, 1886, and 
~ 1887, the first being chosen as being a year of maximum sun-spots. The 
calculations were undertaken by Messrs. Robson and Smith (two of Pro- 
fessor Riicker’s advanced students at the Normal School of Science), and 
their results, brought before the Physical Society,? show a remarkably 
close agreement with the corresponding Greenwich results. The greatest 
discrepancy between any curve in which these differences are plotted 
1 See Brit. Assoc. Report, 1885, p. 78. * Phil. Mag., August 1890, p. 140. 
jetta, 
———o 
ee eee 
