1915-16.] The Size of the Particles in Deep-sea Deposits. 233 
its second maximum is larger and falls at higher values of r than the 
corresponding maxima of the curve P for the Atlantic sample. 
5. Plate III, first figure, A. Radiolarian ooze ; Pacific Ocean : lat. 
7° 25' S., long. 152° 15' W. Challenger Station 274; depth 2750 
fathoms. Mean specific density 202. 
The curve for the sample of Radiolarian deposits is notably free from 
any maxima whatsoever in the interval (16'5^-1'1/x) within which direct 
observations have been made. The comparatively large fraction of still 
smaller particles (56‘3 per cent.) may of course have a maximum some- 
where between 0 and — oo ,* although there is no indication of it in the 
curve. 
6. Plate III, first figure, P. Radiolarian ooze ; Pacific Ocean : lat. 3° 48' S., 
long. 152° 56' W. Challenger Station 272; depth 2600 fathoms. 
Mean specific density P70. 
This Radiolarian ooze is represented by a somewhat less regular curve 
than the former. There is a trace of a maximum somewhere about 2*7 /m, 
and there is a distinct rise at the left-hand side of the curve. 
7. Plate III, second figure. Blue mud ; Atlantic Ocean : lat. 38° 34' N., 
long. 72° 10' W. Challenger Station 45 ; depth 1240 fathoms. 
Mean specific density 2 ’38. 
In the rectilinear shape of the right-hand part this curve resembles 
somewhat that for the first Radiolarian ooze (5). Only a faint tendency to 
a maximum at about 12 fi is to be seen. The amount of very fine particles, 
r<0-8ju, is seen to be surprisingly high. Whether a maximum is really 
hidden in this uninvestigated part of the curve it is of course at present 
impossible to say. 
To draw any definite conclusions of a general character from these 
curves appears to be premature. It is, however, already obvious that a 
promising field for future research is opened by the new method, which 
enables us to define sharply such an important character of the bottom 
deposits as the size of their particles. This result will no doubt have 
important bearings on various interesting problems, such as the origin of 
the deep-sea deposits and their rate of deposition. 
Attention may also be called to one interesting fact. One would 
a priori expect the deposits from the largest depth to be relatively richest 
in very fine particles. This is, however, not the case, as is particularly 
* Observe that log r — 0 and log r = — oo correspond respectively to r = 1 fj.fi and r — 0. 
