96 
Proceedings of Royal Society of Edinburgh. [sess. 
water taken in January 1890 from the same spot, and having a 
slightly lower specific gravity, exerted little or no solvent action on 
the same corals. These remarks also apply to waters taken from near 
shore at North Berwick and Granton in the summer of 1889 and 
January 1890. The lower specific gravity of the winter waters may 
be regarded as, to some extent, reducing the solvent power ; but 
this is more probably to be attributed to the absence of free car- 
bonic acid, that is, carbonic acid in excess of what is required to satu- 
rate the free base in the sea water as normal carbonate (CaC0 3 ). To 
test this point, carbonic acid was added to one of these winter 
waters, but in quantity not sufficient to destroy its alkaline character. 
Powdered carbonate of lime was then added to this water, as well 
as to another portion of the water to which carbonic acid had not 
been added, and both samples were allowed to remain under exactly 
the same conditions for fourteen hours. It was found at the end 
of this time that the water to which no carbonic acid had been 
added had not taken up any of the carbonate of lime, while the 
water to which carbonic acid had been added, under the conditions 
above stated, had dissolved an appreciable amount. 
These results appear to indicate that there is more carbonic acid 
in summer than in the winter waters in our latitude, due probably 
to the increased activity of animal life, and although it may be 
insufficient to form bicarbonate with the free base present, such 
waters have a distinctly more powerful action on carbonate of lime 
structures, the greater the quantity of carbonic acid they contain, 
and especially so when the quantity is more than would form a 
sesqui-carbonate. 
i j 1 
! 
I 
case our experiments have shown that alkaline sea water will dis- 
solve up carbonate of lime in addition to what it already contains, 
and that the rapidity with which this is effected depends on the 
* See Dittmar, Phys. Chem. Chall. Exp . , Part I. 
