320 
THE VOYAGE OF H.M.S. CHALLENGER. 
characters to admit of even an approximate classification as to their origin. Among these 
are magnetite, black mica, apatite, epidote, zircon, delessite, and zeolites, such as analcim 
and chabasite. Some of these, as epidote and zircon, would not likely be found in any 
abundanee among the debris of recent rocks ; their presence, however, is possible. As to 
the secondary minerals and products of alteration, like glauconite, oxides of iron and 
manganese, zeolites, phosphates, and carbonate of lime casts, they will be considered in 
detiiil in the succeeding cliapter. 
Although it may be difficult to determine the relative abundance of the different 
kinds of mineral particles in each type of deep-sea deposit, still it may be stated gene- 
rally that volcanic minerals, whieli bear distinctly the impress of their origin, are not 
only universally distributed throughout deep-sea deposits as a whole, but that they 
abound in the pelagic deposits properly so called, where they form essential constituents. 
In these pelagic regions the minerals are angular, generally of small dimensions, have 
a relatively fresh aspect, and are attached to vitreous particles or to rocks of volcanic 
origin. In certain cases these same volcanic minerals occur in the free state in 
Volcanic ^luds and Sands close to the coasts, but then the dimensions and physical 
characters permit us to distinguish them from minerals of the same nature found in the 
deposits forming at depths beyond the mechanical action of the sea. 
Some of the figures on the plates at the end of the volume represent the aspect of 
these volcanic minerals in the deposits of the littoral and shallow-water zones. PI. XXVI. 
fig. 5 shows such particles from the littoral zone at the Sandwich Islands, where they are 
almost exclusively composed of broken crystals of olivine ; this uniformity of the minerals 
proves that we are dealing with a deposit from a position in which the action of wind 
and water effects a separation according to specific gravity. A similar separation of 
minerals is never observed in deep-sea deposits, where the elements are much less 
voluminous, as may be seen l>y reference to figs. 1 to 4 on the same plate. PI. XXVII. 
fig. 6 represents rounded grains of quartz, glauconite, tourmaline, and zircon, from Station 
189, 28 fathoms, in tlie Arafura Sea. PI. XXVI. fig. 6 represents the volcanic minerals 
of a sliallow-water deposit off the Admiralty Islands. As in fig. 5 the grains are large ; 
some are distinctly rolled, and among them are plagioclase, hornblende, augite, olivine, 
magnetite, fragments of volcanic glass, palagonite, rounded lapilli, and quartz. PI. XI. 
fig. 2 shows the volciinic mineral particles in a deposit further removed from the coast, 
but not in pelagic conditions j)roperly so called ; these are from a Blue Mud, Station 
237, 1875 fathoms, off Japan. Among the particles are plagioclase, sanidine surrounded 
and enclosed by a blackisli opaque glass, hornblende, augite, little plates of black mica, 
magnetite, and fragments of volcanic glass more or less decomposed. In PI. XXVII. 
figs. 1 to 3, and PI. XXVI. figs. 2 to 4, the characters under which these volcanic 
minerals appear in pelagic deposits arc represented, and may be compared with the 
figures above referred to. 
