364 The American Geologist. December, 1893 
Mr. T. Mellard Reade estimates the area of the Paleozoic formations 
of Europe at 645,600 square miles in the total area of 3,720,500 square 
miles. His estimate of the Paleozoic area is of that which is exposed 
at the present time and does not include that which is concealed be- 
neath other formations. I think it will be a minimum estimate to con- 
sider that an equal area is covered by the later formations, which, with 
that exposed, would give in round numbers 1,290,000 square miles, 
or one-third of the land area of Europe. In North America nearly 
one-half of the total area was covered by the Paleozoic sea; in 
South America it was considerably less; and we know too little 
of the Asiatic and African continents to place any estimate 
upon their Paleozoic areas. I think, howevrr, if we take one- 
fourth of the present land area as the territory covered by 
the Paleozoic seas we shall be considerably within the actual 
amount, even if we add to the surface of the continents the mar- 
gins of the continental platforms now beneath the sea. Deducting the 
one-fourth from the total land area, there remain 41,250,000 square 
miles as the land area undergoing denudation during Paleozoic time. 
It may be claimed that large areas in the archipelago region of the 
Pacific and in the Arctic ocean may have been land areas at that time. 
To meet this, 8,750,000 square miles may be added to the 41,250,000 
giving a total of 50,000,000 square miles as the land area of Paleozoic 
time. 
The estimated areas of the various deep sea deposits of to-day con- 
taining a large percentage of the carbonate of lime, are as follows: 
Globigerina ooze, 49,520,000 square miles, mean percentage of carbonate 
of lime G4.53; Pteropod ooze, 400.000 square miles, percentage of carbon- 
ate of lime 79.20; coral mud and sand, 2,556,000 square miles, mean per- 
centage of carbonate of lime 8G.41. In addition to this, Diatom ooze 
covers an area of 10,880,000 square miles, with 22.96 percentage of car- 
bonate of lime; and the mean percentage of carbonate of lime in the 
Blue Mud and other terrigenous deposits that cover 16,050,000 square 
miles is 19.20. If we consider only those deposits containing over 64 
per cent, of carbonate of lime, we have 52,500,000 square miles, over 
which there is at the present time a deposition of the carbonate of 
lime being made. We have roughly estimated that in Paleozoic time 
the area of the Paleozoic sea, in which deposits were being accumu- 
lated, was over 13,000,000 square miles. It does appear that there is 
any good reason to suspect that the area of deposition of the carbon- 
ate of lime in the open ocean during Paleozoic time was not fully equal 
to that of the present time. Adding this area of 52,500,000 to the 
13,750,000, we have over 6(5,000,000 square miles as the probable area in 
which calcium was being deposited in Paleozoic time. 
Conditions favorable for a rapid deposition of the carbonate of 
lime. The conditions most favorable for the rapid accumulation or 
deposition of the carbonate of lime through organic or chemical 
agency are warm water and a constant supply of water through circula- 
tion by currents; this is shown by the immense abundance of life 
