374 PROFESSOR J. W. JUDD. 



Various coral-reef rocks which have been analysed have yielded somewhat abnormal 

 quantities of magnesium carbonate. Besides the early determination of magnesium 

 carbonate in a rock from " Matea " (Makatea) in the Paumotus, by B. Silliman, Junr., 

 we have a rock from Duke of York's Island, which yielded I'BOB per cent, to 

 Professor Liversidge" ; and a rock from Luamanif in Funafuti which yielded 

 Dr. M. T. CooKSEYt 1'69 per cent, of magnesium carbonate. 



In two specimens brought from Namuka in the Fiji Islands, by Mr. Stanley Gardiner, 

 Dr. Pollard found respectively 6 '7 per cent, and 21 "5 per cent, of magnesium 

 carbonate.;}: The interesting results obtained by Dr. Skeats in his analyses of the 

 rocks of raised reefs from various portions of the Indian and Pacific Oceans which 

 have been made in the Geological Laboratory of the Royal College of Science, upon 

 material supplied to us by Sir John Murray, Professor A. Agassiz, and Professor 

 T. Edgeworth David, are of very great value. § 



The only other case besides that of Funafuti in which it has been possible to obtain 

 specimens collected in actual vertical sequence by boring operations, for the purpose 

 of chemical analysis, is that of the deep boring made in 1895-96 at Key West, 

 Florida. The results obtained by Mr. G. Steiger in the laboratories of the United 

 States Geological Survey, are as follows : — 



Depth in feet. 



Calcium carbonate. 



Magnesium carbonate. 



25 



96-49 



-61 



100 



96-47 



T61 



150 



97-12 



1 -80 



350 



91-91 



3-51 



600 



87-28 



5-25 



775 



83-12 



14-07 



1125 



96-16 



1-80 



1325 



97-31 



1-30 



1400 



98-47 



-63 



1475 



97-29 



1-53 



1625 



96-27 



2-39 



1850 



96-94 



2-35 



2000 



96-48 



2-22 



As will be seen by comparison with the Funafuti results, though there is the 

 marked rise of the magnesium carbonate percentage of 775 feet, there is nothing like 

 so clo.se an approach to complete dolomitisation as is found at Funafuti. 



* ' Journ. Roy. Soc' New South Wales, vol. U (1881), pp. l.')9-162. 

 t Memoir III., Austral. Museum, Sydney, Part 1, p. 76. 

 t 'Proc. Camb. Phil. Soc.,' vol. 9 (1898), p. 468. 



§ Full details on this subject will be found in the Memoir by Dr. Skkats jiuljlished in tlic ' Bulletin 

 of the Museum of Comparative Zoology of Harvard College' (vol. 42, 1903, pp. .53-120). 



