300 SECTIONAL TRANSACTIONS.—A. 
Tuesday, September 1. 
18. Prof. W. F.G. Swann.—An Attempt to detect a Corpuscular Radiation 
of Cosmic Origin. 
19, Prof. E. V. AppLeton.—Some Thermionic Valves Problems. 
20. Mr. R. L. Smrru-Rosze.—The Study of Wireless Wave Fronts by 
Directional Methods. 
1. Principle of operation of wireless direction-finders. 
2. Brief résumé of recent work in direction-finding. 
(a) Errors due to local conditions. 
(6) Diurnal variations. 
(c) Land and sea effects and application to navigation. 
(d) ‘ Flat minima’ and rotating magnetic forces. 
3. Methods for complete determination of the direction of (a) the magnetic force, 
(b) the electric force. 
4. Use of the above methods to study the propagation of waves. (a) Daylight 
conditions and the earth’s conductivity. (b) Night conditions and the theory of the 
propagation of waves. 
21. Mr. N. K. Jonnson.—A Study of the Vertical Gradient of Tempera- 
ture in the Atmosphere near the Ground. 
The paper contains a preliminary discussion of the results obtained from an 
apparatus which gives autographic records of the vertical temperature gradient over 
the height intervals 1-2 m. to 7:1 m. and 1:2 m. to 17:1 m. above the ground. The 
description of the apparatus shows that the temperatures are measured by means of 
platinum resistance thermometers mounted in special housings and kept continuously 
aspirated. The autographic records are made on a ‘ thread recorder’ which utilises 
the out-of-balance current of a Wheatstone bridge network. The records for the years 
1923-4 are discussed. Mean hourly values for each month are shown in a series of curves. 
In winter at midday the mean lapse between lm. and 17m. is 0°7° F. (7.e. 24 times 
adiabatic), whilst in summer it is about 2°5° F. (i.e. 84 times adiabatic). Throughout 
the night of both winter and summer there is a mean inversion of about 1°3° F. between 
the same limits of height. In contrast with these mean values the extreme values 
recorded during each month are given. Between the heights of 1m. and 17m. lapses 
of 5-8° F. (20 times adiabatic) have been found and inversions as large as 120° F. 
Tables are also given showing the frequency of occurrence of gradients of various 
magnitudes. 
A number of selected charts are reproduced, and a detailed discussion is given of the 
various features which they contain, and of the factors which determine the magnitude 
of the temperature gradient in this region of the atmosphere. 
22. Mr. D. Brunt.—Periodicities in Weather. 
The paper gives a discussion of the results derived from a periodogram analysis of 
twelve sets of meteorological data each extending over at least 100 years. The data 
used are temperature at London, Edinburgh, Paris, Berlin, Vienna, and Stockholm ; 
rainfall at London, Edinburgh, Milan, and Padua; and pressure at Edinburgh and 
Paris. The periodograms are given in detail in a paper read (in title) at the Royal 
Society in June 1925. 
It is found that no periods over 10 years in length are common to all the records, 
but some short periods, of lengths between 13 and 60 months, occur in a number of 
temperature records, with sensibly the same phase. An 11-year period, which may be 
the sunspot period, occurs in the Edinburgh temperatures, but in none of the other 
records, though a period of between 22 and 23 years, which may be the double sunspot 
period, occurs in several of the records. 
Each of the periodograms shows a large number of peaks, indicating a large number 
of possible periodic variations, and in view of the difficulty of assigning accurate values 
to the phase and amplitude of each period it is considered improbable that these 
results can be utilised for forecasting the weather at any future time. 
