244 Prof. J. W. Judd—Statical & Dynamical Metamorphism. 
result in dynamometamorphiec action. Such changes, resulting from 
pressures that do not effect movements in the rock-masses, may be — 
appropriately called “ statical metamorphism.” 
The researches of modern physicists are beginning to enable us to 
realize what are the chief factors in these processes which go on at 
great depths within the earth’s crust. The striking experiments of 
Guthrie have shown that there is a perfect gradation between the 
states of fusion and solution, and have enabled us to realise the im- 
portant part played by even small quantities of water or other liquids 
held under great pressure in the deeper and highly heated masses of 
the earth’s interior.’ The researches of Spring, van’t Hoff, Reicher, 
and others have shown the effects of pressure in bringing the mole- 
cules of solid bodies sufficiently close to one another for chemical 
affinity to operate between them; and especially significant to the 
geologist is a recent conclusion arrived at by the first-mentioned 
physicist, that when the particles of a solid are brought into juxta- 
position by the action of mechanical force, the chemical processes 
may go on even after the pressure is removed. ‘Time, it is thus shown, 
may become an important factor in such changes.” And, lastly, Van 
der Waals in his remarkable essay on “The Continuity of the Gaseous 
and Fluid States” has shown that “all bodies can mix with one another 
when the pressure exceeds a certain value.” * 
That at great depths and under the enormous pressures within the 
earth’s crust, the whole substance of solid rocks—crystallized minerals 
and glassy groundmass alike—may be traversed by various liquids 
and gases, I think it is impossible to doubt. In various papers in 
which I have endeavoured to establish and illustrate the theory of 
‘«Schillerization,” * I have shown that rocks, which at any point of 
their history have been deep-seated, have undergone very remarkable 
changes—their minerals having been metamorphosed and trans- 
formed, and their original structure sometimes completely altered ; 
these changes, which have taken place quite independently of any 
movement that the rock-masses may have been subjected to, can there- 
fore be spoken of as statical metamorphism. A striking illustration of 
the truth of the conclusions arrived at by Van der Waals is afforded 
by the fact, that in the interior of rock-forming crystals, we find 
cavities (indisputably formed by solvent action long subsequently 
to the formation of the minerals themselves), containing at the same 
time, various supersaturated aqueous solutions and also carbon-dioxide 
retained in the liquid condition by pressure. 
It may be of interest at the present time to draw a comparison 
1 The bearings of Dr. Guthrie’s researches on geological problems have been 
already pointed out. See this Macazinz, Dec. III. Vol. V. p. 1, 1888. 
2 Amer. Journ. Sc. 3rd ser. vol. xxxvi. (1888), p. 288. 
3 I am indebted to my colleague Prof. Riicker, F.R.S., for calling my attention to 
the valuable researches of Van der Waals,which have had such an important influence 
on the views of physicists. His essay, which was translated from the original Dutch 
into German in 1881, is now about to be issued in English form by the Physical 
Society. 
° Gare Journ. Geol. Soe, vol. xli. (1885), pp. 374-389 ; Mineralogical Magazine, 
vol. vii. (1886), p. 81. 
