Dr, A. Wilmore—Uralite and other Amphiboles. . 363 
Pressure is clearly seen to have been effective in converting the 
diallage into hornblende. The crystals of the former were bent, 
stretched, and partly destroyed. Hornblende is developed along the 
eracks in patches and round the edges. A large quantity of magnetite 
has been developed as the result of the change from diallage to 
hornblende. The extent to which secondary hornblende has been 
produced is a measure of the schistose character developed in the rock, 
until, with complete change of the original diallage to hornblende, an 
amphibolite or nephrite-schist is produced. 
The next contribution to be noticed is that of Harker in his 
Sedgwick Prize Essay of 1888.1 In ch. vi, on Diabase Sills, ete., it 
is pointed out that the augite has fringing growths of hornblende, 
these also traversing it in strings and sometimes extending into the 
decomposed felspar. This secondary amphibole is always in crystalline 
relation with the augite from which or in which it grows. 
The pseudomorphic hornblende is for the most part truly secondary 
in the ordinary sense of the word. In one or two examples, on the 
other hand, there are appearances which suggest that the amphi- 
bolization may have begun before the final solidification of the rock, 
e.g. when a grain of augite is seen partly pseudomorphosed by 
hornblende which is in crystalline continuity with hornblende 
moulding the grain. 
We now come to some of the more important papers from the pens 
of the American petrographers. First among these may be taken 
a paper by G. H. Williams.” This a very suggestive paper. It 
is pointed out that pyroxene and hornblende are two different 
erystallographic forms of essentially the same molecule. Some 
experimental work is reviewed. In 1824 Mitscherlich and Berthies 
melted tremolite at the Sevres pottery works and found that augite 
resulted on slowly cooling. G. Rose in 1831 had performed a similar 
experiment with actinolite from the Zillerthal. Fouqué and Michel- 
Lévy have since corroborated. A second paper by Williams in 1890 
contains important suggestions upon the whole question of secondary 
amphiboles. This memoir is intended as a contribution to the study 
of dynamic or regional metamorphism. 
Of the various types of alteration discussed, uralitization occupies 
a prominent place. It is made to include the derivation of any 
hornblende, fibrous or compact, from pyroxene. In discussing this 
process it is pointed out that though it has often been referred to as 
one of paramorphism itis more than that in many cases. Forehhammer, 
Rose, and Svedmark have shown that when augite changes to fibrous 
hornblende, magnetite and often calcite are separated out between the 
needles. 
Williams pointed out that Harrington, of Montreal, had analysed 
three stages in the alteration from pyroxene to a secondary fibrous 
hornblende, and found that during the change there was a loss of lime 
1 Bala Volcanic Series of Caernarvonshire, Cambridge University Press, 1888. 
* «On the Paramorphosis of Pyroxene to Hornblende in Rocks’? : Amer. Journ. 
Sci., 1884, vol. xxviii, No. 16, pp. 259-68. 
5 “The Greenstone Schist Areas of the Menominee and Marquette Districts, 
Michigan ” : Bull. U.S.G.S., 1890, No. 62. 
