120 WHITE : OATLAND COMPLEX OF IGNEOUS ROCKS. 
Alteration products, besides iron-ores in smaller quantity^ 
and the usual chlorite, are secondary dark brown sphene, develops 
ing in patches, and grains of epidote. As an inclusion of original 
mineral, apatite is usually found. 
The gravimetric proportion of hornblende in the dioritic 
end of the acid facies increases from 1.4 per cent, to 7 per cent, 
of the mass. 
THE EFFECT OF THE INCLUDED BASIC XENOLITHS. 
The above concludes the description of sections of the acid 
rocks in their normal conditions, but two sections of rock wer& 
examined showing the junction of basic xenoliths, caught up in 
the acid magna, with the granitic rock. 
The first was taken from the deepest and most central part 
of the boss that was accessible and the second from the north- 
eastern side of the quarry. Macroscopic ally the former showed 
a rounded, the latter, a sub-angular outline. 
The former (Plate VIII., Fig. 1) was found to consist of an. 
allotriomorphic aggregate of minute chlorite, muscovite, calcite^ 
epidote, quartz and iron-ores. Of the original minerals, biotite 
preserved the best forms with epidote enclosed. There were 
also traces of medium-sized (about .8 mm. by .8 mm.) augites- 
now as chlorite, epidote and calcite, also some twinned horn- 
blende and a patch of prismatic fresh-looking actinoHte having 
the outline of a cross-section of hornblende. The quartz was 
in very fine threads Avhich extinguished simultaneously over very 
small areas and were crowded with minute inclusions of the 
other minerals. 
In the other section, confining one's attention to the ap- 
parent effect of the xenolith on the character of the minerals 
in the acid portion of the slide, it was observed that the quartz 
contained some unusually large crystals of iron-ore, that the 
amount of plagioclase present was abnormally large while one 
crystal of augite occurred — probably a xenocryst, with a some- 
what irregular shape. Its average breadth was 1.2 mm. It 
was mostly uralitized, but chlorite was also present in quantity^ 
and practically no trace of the original cleavage remained. A 
broad border of hornblende surrounded the kernel. 
