498 
[August, 
The Constitution of the Earth. 
are in the case of coal and lime, at least temporary addi- 
tions is beyond dispute. The coral zoophyte has the power 
of secreting lime from the waters of the ocean, with which 
it builds up reefs of vast thickness, and entire islands are 
thus created. As the result of the Challenger Expedition, it 
has been discovered that the minute shells of microscopic 
animals which live at or near the surface are constantly 
being showered down upon the bottom of the ocean, where 
they are ultimately transformed into limestone and iron- 
stone. An estimate of the enormous extent of this deposit 
may be formed by reference to the fadt that the ocean covers 
three-fourths of the entire globe. Upon the mechanical 
theory of the formation of the earth, it is assumed that the 
lime thus deposited was previously held in suspension in the 
water ; but the chemist informs us that salt,. not | ime > 1S 
the chief ingredient of sea-water. This deposit of lime has 
been going on for millions of ages, and there is no reason 
to believe that the rate of increase is at all diminishing. 
Moreover, Sir Wyville Thomson concludes that the red 
clay ’ is not an additional substance introduced irom with- 
out ” but “ is produced by the removal, by some means or 
other, over these [deep] areas of the carbonate ol lime 
which forms probably about 98 per cent of the material o 
the ‘ globigerina-ooze.’ ” . r 
The natural inference is that water, like every othei iorm 
of matter of which we have any real (as contrasted with 
theoretical) knowledge, is undergoing a constant change, by 
which lime, iron, salt, and numerous other substances, are 
constantly being developed or evolved ; such evolution being 
the result of general or special changes of circumstances to 
which water is continually being subjected. The theory o 
the mechanical circulation of water, instead of being founded 
upon fadts, is largely a creation of the imagination, in 
place of being immutable or unchangeable, water is one ol 
the most unstable substances of which we have any know- 
ledge. Under mere changes of temperature, it (that is, the 
abstract article) is alternately a vapour, a liquid, or a solid ; 
under some conditions it becomes putrid, whilst under others 
it forms the chief substance of the growing plant or the 
living animal. In the human body it is an important ele- 
ment in the various processes by which upwards ol mty 
more or less stable substances are formed. We have, 
indeed, no reason to believe that water is an exception to 
the other various forms of matter of which, through the 
senses, we have any conscious knowledge. As a fact, it 
falls upon the earth to a depth which has been estimated at 
