56 REPORTS ON THE STATE OF SCIENCE.—1913. 
boom recording North-South motion was as sensitive or more sensitive 
than the one recording East-West motion. Notwithstanding this, the 
amplitudes for East-West motion were usually greater than those for 
the North-South motion. 
If, instead of comparing boom displacements measured in milli- 
metres, we convert these into angular units, the conclusion arrived at 
is that East-West tilting is usually greater than that at right angles. 
VII. On the Direction in which Earthquake Motion is most easily 
propagated. 
In the British Association Report for 1908, p. 74, I discussed 
the direction in which megaseismic motion is most freely radiated. 
Two general conclusions at which I arrived were, first, that the motion 
of large earthquakes travelled farther westwards than it did eastwards, 
and, second, that the range of motion across the equator was shorter 
than it is to the East or West. 
In the following note this inquiry has been extended to four groups 
of earthquakes, the members of each group having origins in the same 
district. Each earthquake is designated by a number corresponding 
to entries in the Shide Register, in the Circulars issued by the British 
Association, and also in a-Catalogue published in the Report for 1912, 
nti 
4 District No, 1.—West Coast of Central America, or approximately 
90° W. 5° N. 
The earthquakes considered are Nos. 806, 1164, and 1450. As 
there are only three members in this group no single station can have 
more than three records. 
At 11 stations lying northwards from this origin 25 records were 
made, or on the average 2°2 records per station. At five stations lying 
to the south of the origin eight records were obtained, the average 
therefore being 1°6 per station. 
Inasmuch as all stations within 60 degrees of the origin each 
obtained the possible three records, I find that if these are omitted 
when comparing records obtained in the North with those obtained 
in the South I get the following results :— 
Nine northerly stations recorded on the average two shecks. Four 
southern stations recorded on the average 1°5 shocks. 
T also find that the average distance from the origin of the 11 North- 
lying stations is 98 degrees, whilst that of the five southerly stations 
is 77 degrees. 
From these examinations it would appear that for the three earth- 
quakes considered, two of which were recorded at Batavia, 159 degrees 
distant from the origin, that motion was transmitted more freely 
towards the North than in the opposite direction. 
If we compare the transmission of motion eastwards with that 
which is transmitted towards the West we obtain the following :— 
At 11 eastern stations 19 records were obtained, or an average 
of 1°8 per station. 
At eight western stations 17 records were obtained, or an average 
of 2°1 per station. 
