DEEP-SEA EXPLOKATION. 
397 
THE RECOGNITION OF MARINE DEPOSITS. 
Having long felt the need of some simple and practical suggestions for the recog- 
nition of the various kinds of sea bottom, I api)ealed, through the good oflices of the 
United States Fish Commission, to Dr. John Murray, of Edinburgh, Scotland, reriuest- 
ing him to formulate such brief and practical rules as would enable the marine 
surveyor to recognize the general character of deposits encountered in deep-sea 
exploration. In response, he kindly contributed the following comprehensive descrip- 
tion of the various marine deposits, and methods of distinguishing them: 
Tlie marine surveyor will rentier excellent service to science by carefully examining and pre- 
serving for future study tlie saiuples of marine deposits brought up from various dejjtlis and positions 
on the ocean’s floor during sounding and dredging operations. Eeccnt investigations with reference 
to the composition and distriljution of deep-sea deposits have led to important generalizations in geol- 
ogy and physical geography. It may be stated generally that the marine deposits found in shallow and 
deeii water near shore are for the most part made up of mineral particles and detrital matters washed 
down from the dry laud or torn away from coasts by the action of waves and currents, and hence 
called terrif/cnoiis deposiU. 
On the other hand, marine dejmsits on the floor of the ocean at distances beyond 100 or 200 
miles from laud are for the most jiart made up of calcareous and siliceous shells, secreted by organisms 
in the surface waters, which have fallen to the bottom; the mineral particles and clayey matter 
associated with these shells appear likewise to have, for the most part, fallen from the surface and to 
have beeTi derived from floating pumice aud volcanic and other dust showers. These deposits are called 
pelagic deposits. There is a great variety in these two great classes of dexiosits, and in jiassing seaward 
there is a gradual transition from the one to the other class. In those regions of the ocean toward 
the Arctic and Antarctic which are affected by floating ice the line of dcmarkation is further com- 
plicated by continental rock fragments and minerals being carried far to sea and deposited on areas of 
the sea bed which would luit for this circumstance be occupied by xiurelj^ X)elagic deposits. Phosjihatio, 
glauconitic, and calcareous concretions are more or less characteristic of terrigenous dex>osits, while 
manganese nodules, sharks’ teeth, carbones of cetaceans, cosmic dust (magnetic sjAiernles containing 
nuclei of native iron and nickel), and zeolitic crystals are sometimes abundant in jielagic dejmsits. 
In examining a sample of a marine deposit the surveyor should note its color and any evidence of 
stratification into different layers, as well as the size of any mineral or organic jiarticles as observed 
by the naked eye. If a portion of a sample be shaken up in a bottle with abundance of water the 
larger organic aud mineral jjarticles can be separated from the amorphous clayey and calcareous 
matter by decantations. If, after the water is i)oured off the larger particles, they be treated with 
a little 8j>irits of wine and then a match be applied, the sfiirits of wine will burn away and leave 
the particles dry, so that they may be easily examined with a louj) or low jiower of the microscope. 
The calcareous particles are usually of a white color, and consist, for the most juirt, of Foraminifera 
( Glohigerina) or Pteropod shells. The former are more or less roundish in form and the largest seldom 
over one-thirtieth of an inch in diameter. The Pterox>od shells are larger but much thinner than the 
Foraminifera. In the very deepest deposits the Globigerin;© are all removed, apparently owing to 
the solvent power of the water through which they have fallen. At lesser dejiths the thinner 
Pteropods disax>pear from the deposits before the Glohigerina; it is therefore imxiortant to note the 
Xwesence or absence of these twoylasses of shells in deep-sea dex)Osits. The siliceous organisms, such as 
Diatoms aud Radiolarians, are recognized by their trausiiarent appearance and sharxi, clean-cut edges. 
If a jiortion of a sample be treated with dilute hydrochloric acid (1 part acid to 10 jiarts water) 
all the calcareous particles may be removed, and the mineral particles can thus be more conveniently 
examined. By this process also a rough estimate may be formed of the quantity of carbonate of lime 
in the sainjile, aud this is one of the most important xioints in classifying dejiosits. The jmrticles of 
quartz and felspars making nji the larger x>art of terrigenous de^iosits near land are usually rounded, or 
can be recognized by their fractures and transxjarent ajipearance. The volcanic X'articles in i)elagic 
deiiosits are usually of a darker color, with the excei)tion of the sidintcred fragments of j>umice or 
volcanic glass. Particles of peroxide of manganese, so fre(pient in the red clays and other iielagic 
deposits, can at once be recognized by treating with a small quantity of xmre hydrochloric acid in a 
