THE CHEjMICAL EXAMINATION OF THE MATERIALS FROM FUNAFUTI. 381 



cent, upwards of magnesium carbonate, until at last we find materials in which the 

 calcium carbonate has entirely disappeared. As the amount of mixed carbonates in 

 the mud diminishes, the proportion of magnesium carbonate to calcium carbonate 

 is found to rise. 



The analyses made of the laminated clays for the Geological Survey of Sweden 

 afford the means of making a very exact comparison of the changes taking place as 

 we proceed from north to south, from Gefle to the south of Stockholm, that is, going 

 farther and farther from the Silurian limestone of Bothnia. The results are so 

 striking and conclusive that I transcribe the table as given by Hogbom, the localities 

 in which are situate from north to south : — 



Localities. 



Percentage of 

 calcium carbonate. 



Percentage of 

 magnesium 

 carbonate. 



Percentage of 



magnesium to 



calcium carbonate. 



Number of 

 analyses. 



Leufsta 



Orbyhus 



Salsta 



Upsala 



Sigtuna 



Fano 



Sodertelje 



Hoi'ningsholm .... 



32-0 

 23-0 

 21-7 

 17-8 

 11-4 

 11-9 

 7-6 

 3-3 



1-2 

 1-4 

 1-5 

 1-3 



0-8 

 1-9 



2-8 

 1-2 



3-7 



6-1 



6-9 



7-2 



7-0 



16-0 



37-0 



36-0 



14 

 6 



10 

 8 



29 

 9 

 9 



17 



These analyses show conclusively that as the detritus from the Silurian limestone 

 is carried out into the Baltic, the soluble constituents are gradually dissolved out of 

 it, but that in this solvent action the removal of calcium carbonate goes on much 

 more rapidly than that of the magnesium carbonate, so that a material becoming 

 gradually richer in the last-named constituent is formed and left behind. 



The observations made in the "Challenger" and other deep-sea explorations — 

 which have been discussed in the memoirs of Sir John Murray, Professor Benard, 

 Mr. Robert Irvine* and others — prove conclusively that, as materials descend into 

 the deeper parts of the ocean, calcium carbonate is being continually abstracted by 

 the solvent action of carbon dioxide. This is well illustrated by the table on the 

 next page given by Murray and Irvine on the proportion of carbonates in deep-sea 

 deposits, which are based on the " Challenger" analyses. 



The study of deep-sea oozes all over the world has amply verified the results 

 obtained during the voyage of the " Challenger," as to the constant solution of the 

 skeletons of organisms consisting of calcium carbonate in their descent from the 

 surface waters to the lower depths of the ocean. 



* Murray and Eenard, " Challenger " Reports, 'Deep Sea Deposits,' (1891); Murray and Irvine, 

 'Roy. Soc. Edin. Proc' (1889), vol. 17, p. 89; Murray and Irvine, ' Roy. Soc. Edin. Trans.,' vol. 37, 

 (1893), p. 481. 



