3o8 
The American GcolOilist. November. 1904. 
chute southwestward. And yet, as the flowage of water is un- 
der gravitative stress, it must be remembered that it will take 
a consicierable difference in head for a fresh water to move or 
balance water with a specific gravity of (1.1898) a fifth more. 
However, the Keweenawan series consists mainly of a great 
series of lava flows, many of them over 100 feet thick. ( See 
as an illustration of this, the section of Tamarack shaft Xo. 5, 
and correlated beds elsewhere given.) They are not likely to 
have lost heat for a long time after their effusion, in fact very 
likelv not before their burial under succeeding flows* so that 
for thousands of years the remnant heat of the effusions and 
the heat of the later intrusions may have aided the circulation, 
and particularly the solvent action of the water, as Van Hise 
(pp. 300, 346, 774), but more particularly J. f. Kemp and 
others have insisted. And yet the accumulation of copper in 
the Nonesuch belt of sandy shales, made up of lava and sand, 
would indicate that it is the chemical character of the lavas 
rather than their heat which is of most importance. The 
source of the copper Pumpelly considers to be stilphides orig- 
inally deposited and bleached out and reduced by the ferrous 
iron. This may be so, and yet it is strange that we see so 
little of sulphides in the original rock ot of sulphates in the 
secondary minerals. I have seen some fine selenite from the 
* In the succession of flows noted in the Isle Royale drill cores of Vol. VI 
and the Tamarack shaft, and other sections studied if there had been a long 
interval between the flows and they had been exposed to air, the amygdaloids 
would have decayed to red clays and iron ores, and if they had been loflg 
enough under water there would have been more or less deposition As is 
obvious from the Tamarack section, there is but very little deposition, and 
while there may have been some contemporary decomposition of the amygd- 
aloids — in fact probably has been, and it may have helped in the copper concen- 
tration, yet in very many cases, it is clear that it did not progress far belore 
the next flow came. In fact in some cases an effect on the marginal grain of 
the underlying flow is indicated. Now, for illustration's sake, if (p. 24-5 of the 
Isle Roj-ale report, Fouque and Levy's observations) an ophite cooling in 
about six days has augite grains 0.03 square millimeters in area, then one 
which has them about 50 square mm. in area. like the Greenstone 120 feet from 
the wall, would take about (6x,5t -03) 10,000 days before it had actually con- 
solidated, that is, it would be between twenty and thirty years before the 
center of a sheet 24-0 feet thick had fully consolidated, and it would still be red 
hot. But the increase of the grain of the augite clean to the center shows that 
it must have been during a very early stage of cooling, and at a glance at 
Plate IV, of the same report shows that after more than ten times that lapse 
of time say, 200 to 300 years, the temperature at the center would still retain 
something like an eighth of its original excess of temperature over the country 
rock. The temperature toward the margin decreases, of course and the total 
amount of calorics yet left in the flow will be readily found by integr.iting 
equation (1 1) or (12) of the Isle Royale report. Of course the above figures 
make no pretense to accuracy. We have no right to apply Fouque and Levy's 
observations on the grain of a rock of one composition of( hand to another. 
Yet the order of figures is likely to be the same, and it is plain that if the 
Tamarack cross section has some fifty flows, and this section only represents 
a third or less of the whole pile of flows thus rapidly piled on each other there 
may have been temperatures near boiling ten thousands of years after the 
formation of the pile, during all of which time the zeolites we now see may 
have been forming. Obviously, too, there will be a large amount of energy to 
promote aqueous circulation. 
