ON SEISMOLOGICAL INVESTIGATIONS. 15 
Observations of PR, are fairly numerous beyond S—P=542 seconds 
(say A=69°), but only three have been found for smaller values, viz. : 
S—P = 487s., 363s., 360s. 
Say A = 59°, 38°.5, 38°.0, 
according to adopted tables. Further scrutiny is of course desirable 
but the evidence is so far satisfactory. 
Of PR; and PR, little more need be said at present than that they 
do not fall near enough to 8 to be confused with it, while PR, probably 
lies beyond 8. The rough minima in A for their appearance are : 
PR, PR, PR, PR, 
A= 60° Ti 94° 111° 
Ss. 8s. s. 8s. 
Time = 896 1152 1408 1664 
S (Tables) = 1103 1309 1496 1657 
S (corrected) = 1102 1300 1474? = 16372 
The above notes are obviously tentative and incomplete, but they 
represent the result of a good deal of work by the method of trial and 
error, and may serve to show possibilities. Especially is it hoped that 
they may show the importance of an identification of the phenomena 
through more accurate tables of P and 8, on which the main computing 
strength of the Shide organisation is being concentrated for the present. 
It may be that there are too many variable elements to make great 
accuracy possible, but experience of working with the residuals suggests 
the contrary view, which is at any rate worth thorough testing, even 
it the ultimate result be disappointing. 
Preliminary Report on Tides and Tidal Currents. 
By H. Lams and J. PRouDMAN. 
Ir seemed most important in the first place to obtain a sort of con- 
spectus of what has been done and what is in progress, in the way 
of observation and reduction, in various parts of the world. Owing 
to the circumstances of the time our attention has been mainly confined, 
so far, to work done in the British Empire and in the United States 
of America. As regards Great Britain, the more accessible literature 
has been consulted, whilst for India, Canada, Australia, New Zealand, 
and the United States valuable information has been furnished by 
various authorities, to whom special acknowledgment will, it is intended, 
be made in a more complete Report. 
It is proposed in the future Report, or Reports, to give an account 
of the work done in the countries named, together with a critical 
examination of such points as appear to call for it. 
In the course of the survey so far made, various suggestions have 
naturally presented themselves, some of which may indicate lines of 
research. The following may be mentioned :— 
1. While the tide-tables as at present produced appear to be adequate 
for practical needs, the possibility of improvement should not be left out 
c2 
