99 
oxides, which are much decomposed, are in part titaniferous, as 
shown by their peculiar club-shaped forms so characteristic of 
menaccanite. Moreover, the pulverized rock gives a distinct re- 
action for titanium, after prolonged digestion with hydrochloric 
acid. The green melaphyr differs mainly in carrying a larger 
proportion of epidote and in the feldspars having undergone the 
viriditic alteration. The amygdules of the rock show first a 
zone of epidote, and interiorly quartz, feldspar and chlorite. 
A typical sample of the melaphyr from this area, non-amygda- 
loidal and carrying no free quartz, yielded on analysis 41.89 per 
cent. of silica. 
First Melaphyr, Western Area.—The structural features 
of this rock are greatly obscured by decomposition, but after 
the examination of several sections I am disposed to place it with 
the melaphyrs. The microscope shows it to consist of a large 
number of greatly decomposed porphyritic plagioclases imbed- 
ded in a groundmass so filled with secondary decomposition 
products that its original character is wholly obscured. The dull 
green macroscopic areas are epidote resulting from the feldspathic 
decomposition. The original iron-magnesian constituents have 
quite disappeared, even their outlines being no longer recogniz- 
able. I assign the rock to the melaphyrs with consider- 
able hesitation. Chemical analysis shows its basic character, 
three samples from different localities affording the following 
percentages of silica: 47.29, 47.97 and 51.05; the latter, at 
least, probably including some free secondary quartz. 
Porphyrite. 
The rock which I here have called porphyrite differs from 
the melaphyrs in showing under the microscope a larger pro- 
Portion of irresolvable ground-mass, in being of a more pro- 
nounced porphyritic structure and in never so far as observed 
being truly amygdaloidal. They are also more compaet and 
fresh appearing and show in none of the sections examined 
