922 
THE VOYAGE OF H.M.S. CHALLENGER. 
Messrs. Murray and Renard arrive at the following conclusions as the result of their 
investigations of the deep-sea deposits : — r Muds and sands are situated at various depths 
at no great distance from the land, while the organic oozes and red clays occupy the 
abysmal regions of the ocean basins far from land. Leaving out of view the coral and 
volcanic muds and sands which are found principally around oceanic islands, blue muds, 
green muds and sands, and red muds, together with all the coast and shore formations, 
are situated along the margins of the continents and in enclosed and partially enclosed 
seas. The chief characteristic of these deposits is the presence in them of continental 
debris. The blue muds are found in all the deeper parts of the regions just indicated, 
and typically near the embouchures of rivers. Red muds do not differ much from blue 
muds except in colour, due to the presence of ferruginous matter in great abundance, 
and occur under the same conditions as the blue muds. The green muds and sands 
occupy, as a rule, portions of the coast where detrital matter from rivers is not apparently 
accumulating at a rapid rate, viz., on such places as the Agulhas Bank, off the east coast 
of Australia, off the coast of Spain, and at various points along the coast of America. 
“ The region occupied by terrigenous deposits extends from high water mark down, it 
may be, to a depth of over four miles, and in a horizontal direction from 60 to perhaps 
200 miles seawards, and includes all inland seas, such as the North Sea, Norwegian Sea, 
Mediterranean Sea, Red Sea, China Sea, Japan Sea, Caribbean Sea, and many others. It 
is the region of change and of variety with respect to light, temperature, motion, and 
biological conditions. In the surface waters the temperature ranges from 80 ° in 
the tropics to 28 ° in the polar regions. Below the surface, down to the ice-cold 
water found in some places at the lower limits of the region in the deep sea, there is in 
the tropics an equally great range of temperature. Plants and animals are abundant 
near the shore, and animals extend in relatively great abundance down to the lower' 
limits of this region, which is now covered by these terrigenous deposits. The specific 
gravity of the water varies much, owing to mixture with river water or great local 
evaporation, and this variation in its turn affects the fauna and flora. In the terrigenous 
region tides and currents produce their maximum effect, and these influences can in some 
instances be traced to a depth of 300 fathoms, or nearly 2000 feet. The upper or 
continental margin of the region is clearly defined by the high water mark of the coast 
line, which is constantly changing through breaker action, elevation, and subsidence. 
The lower or abysmal margin is less clearly marked out ; it passes in most cases 
insensibly into the abysmal region, but may be regarded as ending -when the mineral 
particles from the neighbouring continents begin to disappear from the deposits, which 
then pass into an organic ooze or a red clay, 
“A Pteropod ooze is met with in tropical and subtropical regions in depths less than 
1500 fathoms and a Globigerina ooze in the same regions between the depths of 500 and 
2800 fathoms. These two deposits occupy about 110 ° of latitude between the two polar 
