of Edinburgh, Session 1883-84. 
499 
instrument to the determination of the species of extremely fine, 
loose, and fractured particles. Again, the examination of these 
deposits is rendered difficult by the presence of a large quantity 
of amorphous mineral matter, and of shells, skeletons, and minute 
particles of organic origin. It is also to be observed that 
we have not to deal with pure and unaltered mineral fragments, 
but with particles upon which the chemical action of the sea has 
wrought great changes, and more or less destroyed their distinctive 
characters. 
What still further complicates these researches is the endeavour 
to discover the origin of the heterogeneous materials which make 
up the deposits. These have been subjected to the influence of a 
great number of agents of some of which our knowledge is to a great 
extent still in its infancy. We must take into account a large 
number of agents and processes, such as ocean currents ; the dis- 
tribution of temperature in the water at the surface and at the 
bottom; the distribution of organisms as dependent on temperature 
and specific gravity of the water; the influence of aerial currents; 
the carrying power of rivers; the limit of transport by waves; the 
eruptions of aerial and submarine volcanoes ; the effect of glaciers 
in transporting mineral particles, and, when melting, influencing the 
specific gravity of the water, which in turn affects the animal and 
plant life of the surface. It is necessary to study the chemical 
reactions which take place in great depths ; in short, to call to our 
aid all the assistance which the physical and biological sciences 
can furnish. It will thus be understood that the task, like all first 
attempts in a new field, is one of exceptional difficulty, and de- 
mands continued effort to carry it to a successful issue. 
In presenting a short resume of our methods, of the nomen- 
clature we have adopted, and of the investigation into the origin of 
the deposits in the deep sea and deeper parts of the littoral zones, 
we offer it as a sketch of our research, prepared to modify the 
arrangements in any way which an intelligent criticism may 
suggest. 
Before proceeding to a description of methods and of the varieties 
of deposits, with their distribution in modern oceans, we will 
briefly enumerate the materials which our examination has shown 
take part in the formation of these deposits, state the origin of these 
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