GEOLOGICAL SOCIETY OF DUELIST. 
173 
this difference of specific^ gravity be caused by temperature, by the 
matter held in solution, or by any other thing; the effect is the same, 
namely, a current. 
jSTow, suppose one sea to have held carbonate of lime in solution, 
and a neighbouring sea, carbonate of magnesia, then, according to Maury’s 
theory, a surface and under-current from one sea to the other must have 
been established, by reason of the difference of specific gravity of the 
two seas,—the specific gravity of magnesia being greater than that of 
lime; and these currents must have lasted so long as that difference 
existed, which may have been for thousands of years. 
Thus carbonate of magnesia may have flowed into the one ocean, and 
carbonate of lime into the other, till equilibrium was set up between 
them, which would have occurred on the proportions having become 
one to one, or, in other words, when they had mingled together, and 
gained the ratio to form magnesian limestone; and then an age of tran¬ 
quillity and subsidence may have commenced, during which the mixed 
carbonates may have been deposited at the bottom of the sea, and our 
dolomites and magnesian limestones have been formed. 
It is well known, however, too, that at this moment an under-current 
is flowing in, and an upper-current running out of the Eed Sea. That 
these currents are caused by other causes than the above is true, viz., 
evaporation; yet the theory is the same, and the result the same— 
namely, a current or currents, and the accumulation of vast quantities 
of solid matter. 
Knowing, then, that these currents and counter-currents have been 
going on, almost unceasingly, in various parts of the world ever since 
we became acquainted with them, and that there is every probability 
of their doing so for ages to come,—may not the suspended matter and 
aqueous solutions of one sea have been carried into and become mixed 
up with those of another, and deposited there in regular strata, and fresh 
matter have been carried in day after day and year after year, 
for a continuation of ages, and have been thrown down upon that last 
formed. 
Assuming, then, that such things possibly occurred, it would fully 
account for the absence of fossils in our magnesian limestone. Carbonate 
of magnesia being detrimental to vegetation and injurious to animal 
life, the Fauna of those seas that contained carbonate of lime, finding 
their provinces invaded by the influx of so dangerous an enemy, and 
driven from their old haunts by the noxious fluid, must naturally have 
sought refuge in other parts of the ocean more congenial to their habits 
and less fatal to their existence. But some few feeble and worn-out 
races, unable, perhaps, to accompany their friends, may have been 
engulfed in the magnesian solution, and not having sufficient strength 
to extricate themselves from it, may have been embedded in its de¬ 
posits. 
The Pbesidext then communicated the following paper:— 
VOL. V.-PEOC. SOC. 2 A 
