F 2
It will be seen that while the annual range of temperature in the Underground Chamber is less than half the range in the open air, the range of humidity is nearly double. Unfortunately, the humidity in the Underground Chamber is highest in the summer months and to reduce it by raising the temperature is expensive; moreover the amount by which the temperature must be raised to reduce the relative humidity to even 70% is excessive; about 11° in 1925. This would produce a very unpleasant atmosphere in the room.
For these reasons no attempt has been made to keep the humidity within reasonable bounds.
II.-METEOROLOGICAL INSTRUMENTS.
Barometers.-The Marvin compensated syphon barometer has worked satisfactorily.
The station barometer No. 1323 and the large Casella barometer were compared with the Observatory Standard on December 2nd and 28th.
Beckley Anemograph.-This instrument was oiled and the orientation of the vane checked once a month.
Dines-Baxendell Anemograph.-The bearings of the vane were oiled and its orientation checked once a month. The spindle of the float was cleaned and oiled once a week.
The Mean monthly results of comparisons with the records of the Beckley Anemograph from 1910-1924 are given in the following table, together with the results for 1925:-
Month Mean 1910-1924 1925 January, 1.94 1.92 February, 1.98 1.88 March, 2.03 2.04 April, 2.05 2.11 May, 2.31 2.41 June, 2.23 2.50 July, 2.36 2.79 August, 2.30 3.08 September, 2.29 3.25 October, 2.21 3.06 November, 2.11 2.64 December, 2.05 2.06 Year 2.13 2.14Page 180
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