A, B. Hunt — The Crystallisation of Oranlte. 403 



the card on which it is scored, as that may serve to light a cigarette. 

 Perhaps the chief difference between golfers and scientists is that 

 golfers always know when they are ' bunkered,' whereas scientists 

 apparently are often unconscious of the fact, and think nothing of 

 teeing their ball in a hazard. A hazard in plain English is 

 a difficulty, which, according to the laws of golf, if encoutitered 

 must be surmounted, and not evaded. Evasion, if detected, involves 

 disqualification ; but gentlemen do not evade. 



"With respect to the general question of the crystallisation of 

 rocks we have this curious paradox, viz., that after a rock had 

 consolidated, and already cooled considerably, at a dry heat, the 

 mere advent of water would liquefy it. This, besides being in 

 evidence, follows from the fact that so many minerals which 

 crystallise at high temperatures in the dry way crystallise at low 

 ones in the wet way. Many of the old geologists took the possi- 

 bility of the access of water as granted, but subsequently this was 

 stoutly denied. However, after the blow up of Krakatoa and of 

 the hot-lake district in New Zealand, the evidence seems to favour 

 the ancients. Considering that many regions are jointed and fissured 

 in all directions, and that earthquakes make fresh fissures, and 

 seeing that a column of water at a depth of 3,000 fathoms weighs 

 about 600 atmospheres, or 9,000 pounds to the square inch, the 

 access of water to highly heated though consolidated rocks seems 

 more probable than otherwise. But if such access ever occurs 

 there must be liquefaction, reconstruction, recrystallisation, and 

 metamorphosis in almost every variety ; and the creation of new 

 minerals too, for the sea-water does not come empty-handed, but 

 charged with the highly important rock-forming minerals soda, 

 potash, magnesia, and lime. But when we come to chemistry at 

 a pressure of 600 atmospheres and upward, we cannot safely afford 

 to ignore the chemists and the physicists, any more than physicists 

 can afford to formulate a theory of granite in defiance of petrologists, 

 as was actually done a few years ago. 



I would desire, vei-y respectfully, to point out the great perplexity 

 caused to students by what may be termed incidental petrology. 

 The whole object of the present paper is to discuss General 

 McMahon's incidental remark — " the beryl is crowded with liquid 

 and gas cavities, the former containing movable bubbles and 

 deposited crystals as well as water" (Rep. Brit. Assoc, 1902, 

 p. 590). 



So far as I am aware, the only record of the occurrence of 

 magnetite in cubes in Great Britain is Professor Bonney's quite 

 incidental statement — " Magnetite, very abundant in minute grains, 

 which, however, evidently are often cubes or octahedra " (Proo. 

 Eoy. Soc, 1892, p. 399). As has been already pointed out, the 

 extremely important question of the derivation of tourmaline was 

 discussed, also quite incidentally, in a mineralogical paper dealing 

 with Luxidlianite. 



Lord Kelvin's theory of granite and basalt, again, was completely 

 incidental to his " Age of the earth." It is, no doubt, incompatible 

 with all previous doctrine on the subject, but with the general 



