31S 
THE VOYAGE OF H.M.S. CHALLENGER. 
Volcanic Sand, 7 of Coral Mud, and 1 of Coral Sand. This enumeration indicates 
the wide, even the universal, distribution of these particles over the floor of the 
ocean. 
Recent Volcanic Minerals in General , — After what has been stated above, there can 
be little doubt as to the mode of origin and relatively recent age of the numerous vitreous 
particles scattered over the floor of the ocean. It has been indicated that the mineral 
particles and the more or less complete crystals, which are mixed with these vitreous frag- 
ments in deep-sea deposits, have in all probability a similar age and origin, having been 
derived from the disintegration of the pumice and lapilli of submarine and subaerial 
eruptions. While this is probably the correct interpretation for the mineral particles of 
those pelagic deposits in which all, or nearly all, the inorganic residue is made up of 
volcanic products, it cannot be held to apply to those deep-sea deposits around continental 
shores, in which the fragments of crystalline, schisto-crystalline, clastic, and organic rocks 
of various ages make up a large part of the deposit. 
With reference to the origin of the mineral particles, we, in all cases, rely principally 
upon their association with larger fragments of rocks containing these minerals in the 
same deposit or in the same region of the ocean. Thus, when we discover in the free 
state crystals of plagioclase and augite, still in part covered by vitreous matter, 
associated in the same deposits with palagonitic lapilli or altered pieces of pumice, we 
conclude that these isolated minerals are of the same age as, and have had a similar 
origin to, the fragments which accompany them. In the same manner, if we find 
orthoclase, mica, or quartz, for example, along with fragments of granite, gneiss, and 
schist, we are led to conclude that the minerals in a free state in the mud have been 
transported by the same agents that have carried the rocks accompanying them, to which 
we assign a continental origin. This distinction has all the more force reinembering 
what has been said as to the universal distribution of volcanic materials in the form of 
pumice, lapilli, and ashes, and the more limited distribution of the terrigenous minerals, 
which are transported only to a relatively restricted zone surrounding continental shores. 
In some cases continental fragments may be carried much further than here 
indicated, and may be mixed with the volcanic fragments w’hich are characteristic of 
pelagic deposits. In these ciises *the distinction between minerals derived directly from 
continental rocks and tho.se derived from volcanic products becomes exceedingly difficult, 
and we must then rely upon the peculiarities which the minerals present, especially the 
siliciites of eruptive rocks, according as they have crystallised in rocks of the ancient or 
of the more recent series. We will point out the distinctive characters which may serve 
as a guide in this chissification, but it must be remarked that these characters have no 
alxiolutc value, and that lx;tween the same species of minerals constituting the two series 
of rocks the diflerences are rather quantitative than qualitative. However, when these 
special details are taken into considenition along with the mineralogical and lithological 
