— 165 — 
formed in the deep-sea muds, little information appears to be available. I have 
not had the opportunity of studying the Challenger and many other memoirs 
on deep-sea investigation, hut the Report of the rrPolan Expedition and notably 
Dr. K. Nulterer's account of his cbemical researches in the Bed Sea were avai- 
lable. He obtained a comparative determination of the organic substances 
dissolved in or distributed as fine particles in the sea-water. Leaving aside the 
Suez Canal and the Halaib coral-reef region, it was found that in the water 
fdtered from the sea-bottom muds of 9.5 localities in the northern Red Sea. 
the mean of the oxygen taken up by one litre of this water was 7.62 cc. From 
the Eastern Mediterranean, the mean of 60 results was 5. 80 cc. In the sea- 
water itself, the corresponding figures were 1.28 cc. to i.58 cc. 
Experiments were also made on the amount of Ammonia driven off as gas 
by boiling with magnesia. It was found that the average differed little in water 
taken just above the bottom (0.077 P^^ litre) and that of the 100 metres 
depth below surface (0.07/1 cc). Owing to greater development of organisms, 
among which may be nitrogen-assimilating micro-organisms, the surface 
waters often show higher figures, 0.20 cc. being noted at the northern ter- 
mination of the Gulf of Suez as against 0.1 3 cc. at the southern end, and 
0.20 cc. on the outer borders of the coral-reef near .ledda. 
Experiments were also carried out to determine the amount of Ammonia 
which was yielded by the oxidation through heating with alkaline solution of 
permanganate of potash, Dr. Natterer specially noting how much more was 
obtained in this way than the amount present free in the original sample. 
In the 25 mud-waters examined, 10 yielded twice as much ammonia on oxi- 
dation, none of these being in the Gulf of Suez, but widely distributed in the 
main Red Sea and Gulf of Akaba. 
6. Distribution of Nitrogen-containing acids — From the observations in 
the Mediterranean and Sea of Marmara it was found that nitrogen-containing 
acids due to oxidation of organic acids can only be collected in quantity in the 
dark sea-depths as salts, where the intermixture of the water-layers is slight. 
In the sea-water exposed to sunlight they disappear, their nitrogen being used 
The lest employed was Irealment with sulphuric acid, zinc iodide, and starch, and noting the 
colouration which took place at the end of two houis. The colour scale adopted was a piu'cly empi- 
rical one. 
