. EEE —————=<<—— 
9 Oy Oe ae ae ee 
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SEISMOLOGICAL INVESTIGATIONS. 207 
It would thus be feasible to collect the records of several observatories for 
comparison without taking up an inconvenient amount of storage space. We 
should at Oxford welcome exchanges of this kind (for days of large earthquakes) 
with observatories that would consider a mutual arrangement. 
During the year Milne-Shaw machines have been despatched to Bombay, 
Rio de Janeiro, Wellington (N.Z.), Cairo, and Hong-Kong. 
Mr. J. J. Shaw has been hard at work all the year on the construction of 
Milne-Shaw machines, and as each approaches completion he has seized oppor- 
tunities for experiment. ‘lhe most valuable and laborious of these experiments 
are referred to later under the heading of ‘ Microseisms,’ but another instance 
is represented in the following note supplied by him :— 
Wanderings of the Zero. 
‘In the Report for the year 1917 attention was drawn to the great difference 
in the stability of two adjacent sites 60 feet apart (at West Bromwich), but 
there was a possibility that the wandering of the zero was an effect of changes 
of temperature upon the instruments. The base of the seismograph is poised 
upon three brass feet, the effect of which might be to tilt the instrument if 
one side of the chamber was warmer than the other. 
‘To investigate this point three feet of invar steel were substituted, but the 
wandering of the zero from day to night continued as before. 
‘An attempt was made to counteract the tilt by using invar on one side of the 
instrument and brass on the other. If any effect was produced, it was too small 
to be noticed.’ (J. J. 8.) 
Just as this Report was going to press, Mr. Shaw sent a further note of an 
important series of observations on the effect of solar radiation. ‘ Yesterday 
was a special day here,’ he wrote on August 4; ‘the sky was intensely blue, 
with huge banks of fleecy cumulus clouds, so that the front of my house was 
at one moment in brilliant warm sunshine, and at another in cool shadow.’ 
He noted the times of transition, and found almost immediate responses of the 
seismograph in the cellar. The matter will, of course, be further investigated, 
and fuller details given later. 
Change of Site from Shide to Oxford. 
The departure from Shide (rendered necessary by the return of Mrs. Milne 
to Japan) and removal to Oxford involves discontinuity, which is liable to 
affect scientific results more or less, sometimes in details which are not realised 
TABLE I. 
Numper or HARTHQUAKES REGISTERED. 
Shide er ihe 2g Oxford r 
1916 1917 1918 1919 1918 1919 1920 
January . 5 6 1 2 2, 2 
February . 7 3 5 3 3 11 
March : 4 4 3 3 2 4 
April . 9 6 2 7 6 2 
May . 6 4 5 10 10 10 
June. 4 6 2 5 9 
July . 2 13 7 7 6 
August 15 5 5 6 10 
September . 6 1 3 10 17 
October 6 3: 8 8 13 15 
November . 9 1 10 7 8 6 
December .- 7 4 4 4 2 16 
Total 80 56 55 74 108 
until too late to remedy the defect. The most noticeable change up to the 
present has been decidedly advantageous, viz. the steadiness of the trace has 
been immensely improved. This is probably not a consequence of change of 
