A. R. Hunt — Superheated Water. 169 



IV. — SUPEKHEATED WaTER. 



By A. E. Hunt, F.L.S., F.G.S. 



rriHE abstract in the Geological Magazine of Professor Beck's 

 J_ paper on ore veins and pegmatites is of great interest to myself, 

 as it deals with two points which I pressed on geologists in 1894 

 and earlier, viz., the crystallisation of vein-minerals out of super- 

 heated water, and the doubtful origin of that water. The special 

 difficulty is raised by the Dartmoor veins, as the water they contain, 

 together with the granites, is sometimes salt and sometimes fresh, 

 and is of all degrees of original supersaturation. I wrote as follows : 



"The question as to the marine or plutonic origin of the brine- 

 inclusions referred to is of transcendent importance in connection 

 with the question as to whether the water ejected by volcanoes is 

 of meteoric or marine origin, or derived from the interior magma " 

 (Geol. Mag., 1894, p. 99). 



Then, referring to the various theories current about the Dartmoor 

 granite, I wrote : 



" It would greatly facilitate further research in the Dartmoor 

 area if the following three points could be definitely decided : — 



" (1) Whether the volcanic hypothesis is tenable ? 



" (2) Whether the chlorides in the quartzes are of marine or 

 plutonic derivation ? 



" (3) An explanation of the immediate juxtaposition of brine and 

 fresh-water inclusions." 



The latter are sometimes within oq^^oo^ of an inch of each other. 

 One of these pairs is figured and described on p. 102 of the paper 

 referred to. 



At the time I wrote, in 1894, I laboured under the extraordinary 

 delusion that I had originated the idea of the marine origin of the 

 brine locked up in veins and granites, having arrived at that 

 conclusion entirely through the i and -^g objectives. I thought it 

 a problem of micro-petrology solely. But Sir Henry de la Beche 

 had actually before 1839 postulated the action of superheated salt 

 water (i.e. "greatly heated water under pressui'e") in deep-seated 

 and therefore " greatly heated " fissures in the earth's crust (Eeport 

 Devon and Cornwall, p. 387). De la Beche's priority of suggestion 

 I fully acknowledged in the Geological Magazine in 1901, in 

 " The Age of the Earth and the Sodium of the Sea," but I never 

 succeeded in making a single convert, and the late General MacMahon 

 assured me with equal kindness and candour that he thought my 

 theory unthinkable. 



I should be well satisfied if I could only establish the first step, 

 viz. the crystallisation of veins and pegmatites from superheated 

 water, as I would trust all the rest to follow. According to 

 Professor Beck this first step is allowed by such distinguished 

 foreign observers as Messrs. Brogger, Eosenbusch, Arrhenius, Vogt, 

 Grubermann, and others. 



In 1889 I wrote that the " brine and salt crystals . . . tell 

 us clearly enough that we have superheated water to deal with, and 



