322 
THE VOYAGE OF H.M.S. CHALLENGER. 
continental rocks over the ocean to considerable distances from their embouchures, but 
icebergs eflect this distribution to a much wider extent than any other agent with which 
we are acquainted. 
In the examination of the deposits collected by the Challenger and other ex- 
peditions, fragments of continental rocks and minerals were rarely if ever found in 
any of the regions of the great ocean basins far from land, except in, or in the 
immediate neighbourhood of, those regions affected by floating ice and icebergs in 
the northern and southern hemispheres. It is true that these fragments of rocks have 
been found some distance beyond the known limits of floating icebergs, but it is 
evident that floating ice must have had a wider extension formerly than at the 
present time. In the Quaternary Period, for example, the great extension of glaciers 
indicates that the icebergs derived from them must have been more numerous, 
while the climatic conditions must have contributed to their wider distribution in low 
latitudes. 
During the voyage of the Challenger, the fragments of ancient rocks and minerals 
were met with in more or less abundance in the following regions : — 
Between Bermuda and Halifax : ^ large block of syenite, diabase, quartziferous 
diabase, basalts ; fragments of gneiss and of mica-schists ; quartzite containing 
tourmaline, zircon, kaolin, chloritic substance ; dolomitic limestone. 
Between Bermuda and Azores : ^ sandstone containing mica ; mica-schist.® 
Between Tristan da Cunha and Cape of Good Hope : * the presence of large 
fragments of quartz, orthoclase, hornblende, tourmaline, and augite, indicates 
that the Challenger here passed over a region occasionally affected with float- 
ing ice. 
Between Heard Island and Melbourne.® During this trip towards the Antarctic 
regions, blocks, pebbles, and fragments of ancient rocks were found to make 
up a considerable proportion of the whole of the deposits, the following having 
been observed : — Granite containing orthoclase, plagioclase, quartz, black mica ; 
granitite containing orthoclase, plagioclase, quartz, black mica, and hornblende ; 
gneiss containing quartz, black and white mica, garnet ; amphibolite with large 
crystals of green hornblende and quartz ; metamorphic quartzite speckled 
w’ith black mica ; fine grained micaceous sandstone, with white mica ; fine 
grained chloritic sandstone ; red sandstone ; slates containing sericite, rutile, 
and quartz. 
Between Tahiti and Valparaiso.® Although the Challenger w^as considerably to the 
> .S<-e pp. 151, 152. 3 See p. 152. 
* The French ship “Talisman” dredged fragments of continental rocks even further to the south and east (see 
Fouijud anti Ls’-vy, Comptts Rendiu, tom. cii. pp. 793-795, 1880). 
• See p. 157. ® See pp. 163, 164. 
See p. 180. 
