172 Notices of Memoirs—Prof. Edward Hull. 
and sanidine; but even in these cases many orthoclase granites 
contain proportionate quantities of the soda felspars such as oligoclase 
and albite, and the decomposition of these components would hasten 
that of the less soluble varieties. 
19. It seems not improbable from certain considerations connected 
with the organic structures of the ancient world, that carbon-dioxide 
was more abundant in the atmosphere of Paleozoic times than at 
present. The enormous quantity of carbon which must have been 
extracted from the air during the Carboniferous period in order 
to the formation of the beds of coal at intervals all over the world, 
seems to favour this view ; and if this be so, then we may suppose 
that previous to the Carboniferous period, the air was highly charged 
with carbon-dioxide, and the process of decomposition on the land 
surface was carried on with even greater rapidity than at the 
present day; but even had this not been the case, it only requires 
a sufficiently long period in order to bring about the chemical 
reactions necessary to the salinification of the oceanic waters. 
20. We are now approaching the conclusion of our enquiry. 
From the examples of closed lakes we can determine the process 
of salinification with the utmost certainty. Throughout greater or 
shorter periods, these lakes have been receiving the waters of rivers 
bringing down, both mechanically suspended sediments and chemi- 
cally dissolved salts, silicates, and carbonates. ‘The sediments are 
precipitated over the bottom of the lakes, and the water being 
carried off into the atmosphere in the form of vapour as fast as 
at enters, leaves behind the dissolved ingredients. These necessarily 
augment in quantity, and ultimately the waters of the lakes become 
Saturated with salts and carbonates, which are then deposited. 
21. Now the ocean is a closed lake of enormous magnitude. 
Throughout all geological time it has been receiving continual 
supplies from rivers, bringing down not only sediment, but salts 
and carbonates, together with free silica, in solution. The sediment 
is deposited over the ocean floor, and generally not far from the 
lands, while the dissolved ingredients are carried by the currents 
into all parts. Meanwhile the ocean surface is constantly giving 
off, particularly over the equatorial regions, enormous quantities 
of vapour, which are carried into the higher regions of the atmos- 
phere, and are precipitated in the form of rain and snow over the 
lands. Part of course falls on the sea again, but the greater 
‘quantity falls on the Jand surfaces, and is returned to the ocean 
in streams charged with a fresh supply of the salts and carbonates 
it had left behind in the ocean.1 he consequence of this process 
must clearly be that the saline ingredients have been increasing 
in the oceanic waters from the earliest periods down to the present 
day. As regards the carbonates of lime and magnesia, and the 
silica which are being carried into the ocean by the rivers, we have 
no difficulty in accounting for their uses. Of these materials, the 
Shells and skeletons of the molluscs, echinoderms, reef-building 
This process of evaporation and supply by rivers is accurately described in the 
Book of Ecclesiastes i, 7. 
