194 
Proceedings of the Royal Society of Edinburgh. [Sess. 
XIX. — Note on a Comparison of Records of Atmospheric Electric 
Potential at Two Stations in Edinburgh. By G. A. Carse and 
G. Shearer, Edinburgh University; and H. Jameson, Royal 
Observatory, Edinburgh. 
(MS. received February 26, 1913. Bead March 3, 1913.) 
The electrograms (continuous records of the atmospheric potential) were 
obtained by means of electrographs of the Kelvin water-dropper type at 
the Physical Laboratory, Edinburgh University, and the Royal Observatory, 
Blackford Hill, and as the inspection of the records showed some remark- 
able similarities, a more detailed comparison of the records was instituted, 
the results of which are given in this paper. 
We are indebted to the Astronomer Royal for Scotland, Professor 
Sampson, for access to the Observatory records. 
In the comparison of the curves considerable difficulty was met with on 
account of the difference in sensitiveness of the electrometers at the two 
stations. Often, when the curves appeared to agree excellently, it was 
found impossible to obtain definite numerical results of this agreement on 
account of the extreme difficulty of picking out with any degree of certainty 
corresponding points on the two curves. 
The plan adopted was to arrange the curves in three groups, A, B, C, 
A containing those which showed good agreement, B fair agreement, and 
C bad or no agreement. This was carried out for the months January to 
June 1912, and the results are given in the following table. All days were 
compared with the exception of those days on which one or other of the 
Table I. 
1912, 
Percentage of 
No. of Curves 
compared. 
A. 
B. 
C. 
January 
55 
36 
9 
22 
February 
45 
36 
30 
20 
March .... 
36 
36 
28 
28 
April ... 
36 
36 
28 
28 
May .... 
52 
31 
17 
29 
June .... 
26 
58 
16 
19 
