Vol. 65.] ANNIVERSARY ADDRESS OF TILE PRESIDENT. cix 



100,270 tons of sodium to the cubic mile, while the underground 

 waters must be much richer. 



In the interior of the volcano, which is beyond the reach of 

 observation, an elevated temperature must play an important part. 



The composition of the water obtained at Honolulu is not stated 

 by Mr. Boultbee ; the shallower wells sunk along the southern coast 

 of Molokai arc extremely rich in sodium-chloride, and their salinity 

 is said to increase with their distance from the centre of maximum 

 precipitation : thus at Kawela the water contains 400 parts of salt 

 to the gallon, at Kaunakalai 800 parts, and at Palaau as much as 

 1540 parts, or even more. Some of the wells in these localities 

 were pumped for a considerable time without increasing the salinity, 

 but it not infrequently happened that on sinking the well deeper 

 sea-water was encountered at depths of 120 to 100 feet. 



If we could argue from the estimate made for the 54 square 

 miles on Molokai to the 0040 square miles which form the total 

 area of the Hawaiian Islands, we should have a total run-off of 

 5146 seconds-feet, and a total subterranean drainage of 11,185 

 seconds-feet. 



The average amount of sodium in the run-off of Hawaii is 24*5 

 parts per million, which gives a total annual discharge of 100,340 

 tons. If we suppose the underground water of Honolulu to have 

 the same composition as the run-off — then, allowing for the extra 

 salinity, this gives 39 '6 parts of sodium per million, and a total 

 annual discharge of 388,800 tons per annum ; thus, by this estimate, 

 489,140 tons of sodium would be contributed annually to the sea 

 by these islands. This may be compared with the amount supplied 

 by some of the rivers of North America : — 



Hawaii 6040 square miles 489, 140 tons of sodium. 



James Eiver 6200 „ „ 21,820 ,, 



Sacramento 9300 „ „ 350,980 „ 



We have no data on which to base even an approximate estimate 

 as to the amount of sodium supplied by other volcanic regions, such 

 as Iceland, with its numerous hot springs and geysers, Polynesia, the 

 East and West Indies, the Philippines and many others. The area 

 of the regions just named is 1,044,500 square miles, or only about 

 J^-th of the entire drainage-area of the world, but 1 of that we 

 have been able to investigate numerically. It is evident, however, 

 that the amount of sodium derived from this fraction might affect 

 our estimates very appreciably. 



Geologists are not perhaps completely agreed as to the precise 

 relative importance of marine and fluviatile denudation, but there 



