ON SEISMOLOGICAL INVESTIGATIONS. 43 
comparatively little value, the records for small quakes being liable 
to errors of various kinds; and from April 1913 onwards a chart 
has been printed showing merely that such and such a quake has 
been observed at a particular station without further details, except 
in the case of a really large earthquake. It is, of course, difficult to 
draw a satisfactory line between large earthquakes and small, but a 
practical procedure was based on the following figures given in the 
April Bulletin :— 
Number of Stations recording an Earthquake : 
Month oo | 
| 5 to 10 | 11 to 20 | 21 to 30 | 31 to 40 41 to 50 | Over 50 | 
| 
a | | | 
January BLN wksareie lh tag ccd Sts) eres 4 2 
February Dia 5 ay 1 0 1 
March . 6 | 9 7 3 2 3 
April. 9 | 13 6 10 4 3 
Total =. .| 28 | 32 21 16 10 9 
According to this table, if attention is confined to those earthquakes 
recorded at thirty-one stations at least, we should get a hundred of 
them in a year; and it was thought sufficient to give full details for 
these. It should be remarked that the stations are no longer Milne 
stations only—the list has been extended to include all those stations 
which send their records to Shide; and it is hoped that this compre- 
hensive collation of results will be found useful. Undoubtedly a 
comparison with tabular theoretical results would increase its useful- 
ness, and it is hoped to undertake such a comparison from January 
1914; but to attempt this for 1913 would have seriously delayed 
publication (already considerably in arrear), and indeed was scarcely 
possible until a tentative discussion such as is given later in the present 
Report had been carried out. 
Notation.—One other change will be made in January 1914. The 
symbols P,, P,, P,, &c., were introduced by Milne, and have been 
used by him throughout his work, although he assented to the change 
to P, S, L, &c., as determined at the Manchester Meeting, 1911, of 
the International Seismological Association. It seemed only a proper 
mark of respect to complete the year of Milne’s death (1913) in his 
notation; but the change to the adopted system will be made from the 
beginning of 1914. 
Visitors.—The station at Shide continues to attract a number of 
visitors, many of them with only a limited knowledge of seismology ; 
their visits naturally make inroads on the time of the assistant-in- 
charge, but it seems undesirable to discourage them at the present 
juncture. The visits of seismologists have naturally been affected by 
Milne’s death; and in the consequent disorganisation the visitors’ book 
was for a time not regularly posted; but we have had the pleasure 
of seeing at Shide Mr. J. J. Shaw of West Bromwich, Mr. E. F. 
Norris of Guildford, Mr. J. Round and Mr. S. B. Round of 
