Cviii PROCEEDINGS OE THE GEOLOGICAL SOCIETY. [May IQO9, 



A remarkable case of a sudden outburst of fresh water into the 

 sea in the vicinity of the south point of Florida is recorded by 

 Raymond Thomassy as having occurred in January 1857. 1 Myriads 

 of dead fishes are said to have been seen floating on the surface in 

 the Straits, and in the open sea boatmen drew their drinking water 

 as if from a well. The outflow is said to have continued for more 

 than a month, as much water being discharged as from the 

 Mississippi itself. 2 



Apart from the continents are the numerous volcanic islands of 

 the Ocean, — in the Atlantic, the long series beginning with Jan 

 Mayen, and passing through Iceland to Tristan da Cunha and the 

 Bouvets, — in the Pacific, many scattered groups, including Fiji, 

 Samoa, and the Hawaiian Islands. These occupy it is true only a 

 comparatively small area ; but they furnish disproportionately large 

 supplies of sodium, owing to their favourable situation as well as to 

 other circumstances. They are watered by an abundant rainfall, 

 the greater part of which sinks into the porous material of the 

 cones, and then flows outwards and downwards, often guided by 

 the lava streams and mantles of ash and scoriae, which are disposed 

 as though with the special design of facilitating a quaquaversal 

 subterranean drainage. The existence of such a drainage is 

 well known. W. Lindgren, 3 after a careful survey of the island of 

 Molokai, estimates the rainfall on one part of the southern slope, 

 54 square miles in area, as equivalent to 194 cubic feet per second : 

 of this (in round numbers) 40 to 56 feet are lost by evaporation, 

 31 to 46 feet run off in streams, and 93 to 124 feet sink into the 

 ground. This water is tapped by numerous wells sunk near the 

 coast. On the northern side of the island, which is much steeper, 

 the proportion of run-off is greater. On the coast in the neighbour- 

 hood of Honolulu the underground water of Hawaii itself has been 

 reached by artesian wells, few of them more than 500 feet deep. 

 They yield 275 millions of gallons per diem., or 0*1094 cubic mile 

 per annum : the salinity amounts to 13 or 14 grains per gallon. 4 



The nature of the volcanic material, much of it being finely 

 divided and in a state of glass, renders it peculiarly susceptible to 

 chemical disintegration. Even the superficial streams of Hawaii, 

 as shown by numerous careful analyses, contain on the average 



1 E.. Thomassy, ' Essai sur l'Hydrologie ' 1857. 



- For most of the preceding instances I am indebted to Elisee Eeclus, ' The 

 Earth,' section 1. London, 1871, cap. xlii. 

 . 3 Waldemar Lindgren, ' The Water-Eesources of Molokai, Hawaiian Islands ' 

 Water-Supply & Irr. Paper No. 77, U.S. Geol. Surv. 1903. 



* Boultbee, Proc. Roy. Soc. N. S. W. vol. xxxvii (1903) p. clxi. 



