28 
during the shearing. Carbon also is directly altered into the schist-making 
mineral graphite, and this fact additionally suggests that it would be stable 
during shear, as the tendency of shear is to eliminate the non-schist-maldng 
constituents. If this be true, then it becomes evident that between 35 and 
45 per cent of the weight of the original tuff was eliminated during the 
shearing process. All the other constituents decreased in relative amount, 
except iron. The iron remained practically constant in Figure 9, although 
Figure 8 shows a slight decrease; but surprisingly enough the ferric iron 
greatly increased, indicating that the shearing process caused oxidation 
of the ferrous iron. Borne of the curves shown by Leith and Mead in 
“Metamorphic Geology” suggest a similar conclusion. Potash suffered 
little or no elimination, presumably because it entered into the stable 
mineral sericite. Lime is the constituent most strongly eliminated, with 
soda second, and magnesia third. Alumina and silica, compared with 
carbon, appear to have been eliminated only to the extent of 25 or 30 
per cent. 
It will be noted from the diagrams that although certain constituents, 
like carbon and iron, exhibit continuous increase with increasing shear, 
and certain others, like lime and soda, are successively decreased, there 
are some whose behaviour is more complex. These, magnesia, potash, 
CO 2 , and water, were eliminated to a considerable extent, but the elimina- 
tion was greatest in the less sheared specimens , and proportional increases 
occurred with more intensive shear. Moreover, in the case of potash and 
magnesia at least, the proportional increase is approximately the same 
as for carbon . The only possible explanation appears to be, that with 
the first pressu res these constituents were converted into the schist-making 
minerals, sericite or other mica, talc, and chlorite, and amounts in excess 
were at once eliminated. The new minerals thus formed were stable 
thereafter, and increased relatively as lime and soda continued to be elim- 
inated by increasing pressures. Just why C0 2 should behave in this 
manner is a puzzle, however, as it is not a constituent of any known schist- 
making mineral. 
The result of the shearing of the greenstones, analyses 7 to 9, is shown 
in Figure 10. Here unfortunately there is no constituent like carbon 
that is reasonably certain to have remained constant. It might be assumed 
that, as in the case of the tuff, 35 per cent or more of the weight was elim- 
inated by shearing; this may well have occurred, as the shear is of approx- 
imately the same intensity as irl the case of the tuff. On the contrary, 
the amount eliminated is probably not regulated by the intensity of the 
shear alone, but also by the relative proportions of the constituents. If the 
exact proportions were present for the conversion of the whole mass into 
micas, chlorites, and other schist-making minerals, none might be elim- 
inated even under severe stress, hence the eliminations may be confined 
to those constituents which are present in excess. In this instance, there- 
fore, it would seem dangerous to assume a greater loss of weight than the 
diagram indicates. Silica, water, and alumina all lie on about the same 
vertical line to the left of the 100-line; and if it be assumed that these 
oxides remained constant, it follows that about 15 per cent of the total 
weight was lost during shear. The loss has been distributed between 
CO 2 , lime, and magnesia, in the order named; presumably, therefore, 
the lime and magnesia were carried away as carbonates. A very small 
