A HISTORY OF CUMBERLAND 
in the central Pacific, as well as in those parts of the Indian Ocean where 
the ocean floor lies at a greater depth than 2,500 fathoms. To under- 
stand the full significance of the fact a brief digression is needed. In 
nearly all the warmer parts of the ocean surface-waters there exist vast 
numbers of minute animals of lowly organization (the Protozoa), some 
of which secrete from the sea water carbonate of lime, which forms the 
harder and outer parts of the creature (the Foraminifera) ; while another 
allied set of minute animals secrete from the fine clay present in all sea 
water corresponding shells of siliceous composition. These latter animals 
referred to are the Radiolaria. When these Protozoa die, their harder 
parts slowly descend through the sea water, and in course of time may 
sink to a great depth below the surface. But as this quiet drizzle of 
shelly matter settles towards the bottom, the sea water begins to exercise 
a solvent effect upon the calcareous shells, the effect increasing with the 
depth below the surface ; while the associated siliceous shells are not 
so acted upon by the water. As a consequence, few, if any, of the cal- 
careous shells survive a descent of more than 2,500 fathoms, while the 
siliceous shells that set out on the same journey with them reach the 
bottom undissolved. In other words, below 2,500 fathoms few or no 
calcareous organisms are to be found, those of siliceous composition alone 
remaining. The Radiolarian Ooze of the present day is found only at 
depths exceeding 2,500 fathoms. Geologists usually reason on the basis 
that principles founded upon facts observed now hold good equally well 
in similar cases in the past. That is to say, a Radiolarian Ooze, what- 
ever its age, denotes a depth at the place where it was found of more 
than 2,500 fathoms. Now, a Radiolarian Ooze of well marked char- 
acter and of considerable thickness, lies close above, and is partly inter- 
stratified with, the deep-sea volcanic rocks just mentioned as contempo- 
raneous with some of the Skiddaw Slate rocks near Keswick. It is quite 
likely that a cherty deposit found in connection with the Skiddaw Slates 
near Ousby may represent this deep sea deposit here. At any rate, we can 
feel sure of this point, that at the period when some of the slates near 
Skiddaw were being deposited as layers of fine clay at the bottom of a 
moderately deep sea, there existed a great oceanic depression only a few 
miles to the north. This again suggests that the old land at this period 
lay somewhere to the south of Cumberland. 
The Radiolarian deposit referred to may some day be detected in 
the Lake district itself. Whether that prove to be the case or not, we 
have in this old oceanic ooze one more of the many proofs that are 
coming to light in various parts of the world, and in connection with 
rocks of all ages, that oceanic areas and continents have really changed 
places, and that, too, more than once at the same spot. 
(c) During the latter part of the time when the oceanic phase of 
geographical conditions prevailed near the site of the English border, the 
parts of Cumberland a few miles farther south began to be the theatre of 
a series of changes of a different kind. A slow movement of upheaval 
of a very local character set in, and there is reason to believe that the 
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