232 Proceedings of the Royal Society of Edinburgh. [Sess. 
which evade actual measurement. If correctly and completely drawn, these 
parts should obviously approach the axis almost asymptotically, and finally 
coincide with it for certain values of r, corresponding respectively to the 
largest and the smallest particle in the sample. The total surface enclosed 
by them would be equal to the shadowed areas in the figures. 
The following deposits were investigated : — 
1. Plate II, first figure. Red clay; Pacific Ocean: lat. 13° 28' S., long. 
144° 30' W. Challenger Station 276; depth 2350 fathoms. 
No data for the mean specific density of these samples being obtain- 
able, I measured it myself by means of a pycnometer : a- = 2T7. 
The distribution-curve is seen to have a well-developed maximum 
corresponding to a radius of 12 ^ — in fact, the most pronounced maximum 
found in any of the curves I have studied. By far the largest part of the 
particles, viz., 89 per cent., are comprised within the comparatively narrow 
limits 1 6/x-5yU, whereas the percentage of very fine particles is quite 
small, 4T per cent., and that of very coarse particles almost vanishing. 
2. Plate II, second figure. Red clay ; Atlantic Ocean : lat. 24° 20' N., 
long. 24° 28' W. Challenger Station 5; depth 2740 fathoms. 
Mean specific density 2 ’03. 
This curve showed marked differences from No. 1. The number of very 
fine particles is much higher, no less than 44’3 per cent, falling below Tl/x, 
so that I have only been able to measure their joint weight after coagula- 
tion. On the other hand, a comparatively large percentage of the particles 
are more or less evenly distributed over the larger sizes, the number 
having r > 16/u being 8 per cent., whereas the Pacific red clay had no 
particles larger than 16yu. 
3. Plate II, third figure. Atlantic Globigerina ooze ; Atlantic Ocean : lat. 
21° 15' S., long. 14° 2' W. Challenger Station 338; depth 1990 
fathoms. Mean specific density 1*72. 
4. Plate II, third figure. Pacific Globigerina ooze ; Pacific Ocean : lat. 
38° 6' S., long. 82° 2' W. Challenger Station 296 ; depth 1825 fathoms. 
Mean specific density 2'28. 
A distinctly new type of curve is found for both samples of Globigerina 
ooze, in spite of the widely different localities from which the samples were 
collected. There are two pronounced maxima separated by an empty space, 
i.e. no particles whatever of intermediate size were to be found in the 
sample. On the other hand, it is seen that the Pacific ooze has its first 
maximum considerably smaller and situated at a smaller value of r, whereas 
