6 MR GOODCHILD ON 
could not be the case. The analyses of river-water and 
sea-water above referred to showed that, whatever quantity 
of bicarbonate of lime any particular river might transport 
to the sea, the water of the sea off the mouth of that river 
showed the characteristic difference in the composition of its 
salts to which reference has just been made. That is to 
say, the percentage of carbonate of lime as compared with 
sulphate of lime in river-water is usually about as 9 of 
the former to 1 of the latter; while in sea-water this is 
reversed, and the proportion of sulpbate of lime to carbonate 
is as 17 to 1. As the absolute quantity of lime in the form 
of carbonate present in sea-water has long been known to 
be so much in defect, it has probably occurred to many 
persons who have given any thought to the matter, as it 
occurred to me, that, by some means or other, the carbonate 
of lime is converted into the sulphate at the zone where 
river-waters meet the sea, and that it is from the solutions 
of swlphute of lime, and not from those of the carbonate, 
that marine lime-secreting organisms first obtain the supply 
of lime which they eventually fix in the solid form. In 
1887 and 1888 I used to offer this as a suggestion worth con- 
sidering, when teaching geology to the students at Toynbee 
Hall. In the meantime, and, of course, quite indepen- 
dently, Mr Robert Irvine, of Royston, near Granton, had been 
thinking over the same facts, and had set to work to find 
out whether the conjecture just mentioned could be proved 
or not. The results of his experiments were most inter- 
esting and instructive, and were given in a communication 
to the Royal Society of Edinburgh in 1889. In these ex- 
periments the author and his fellow-workers proved, beyond 
the possibility of a doubt, that lime-secreting organisms can 
and do obtain their carbonate of lime from almost any lime- 
salts that happen to be in solution—the compound of most 
importance beimg the sulphate of lime. Some papers I 
wrote about the same time, dealing independently with the 
same subject in a speculative manner, were printed after 
Mr Irvine’s, and were, fortunately, delayed in publication, 
so that they came in time for me to acknowledge in print 
the great value of the work, from both a geological and a 
biological point of view, which the gentleman just named 
