By Nevil Story Maskelyne, U.A., F.R.S. 155 
externally a somewhat yellow aspect, that of No. 4 is whiter. The augite is 
browner than in No. 2, generally finer in grain and in smaller amount as a 
constituent of the ground mass than is the case in some others of these diabase 
obelisks. The chlorite is sometimes seen in distinct triangular plates. The 
presence of quartz in some parts of this stone as a constituent is a noteworthy 
feature of it. The crystals are distinctly recognisable and are present in con- 
siderable amount. In other parts the stone seems very free from this ingre- 
dient. 
No. 5 differs from the stone No. 2 for the most part in the somewbat greener 
hue of the augitic constituent. 
No. 6, two recumbent fragments, and No. 7 call for no special remark; they 
resemble Nos. 2, 4, and 5. 
In No. 8, the ilmenite (or magnetite ?) is somewhat prominent as a constituent. 
And this is also true of No. 10, in which the felspar seems very white and 
much decomposed ; the externally greenish hue of the stone being due to the 
augite, and also no doubt to the chlorite. ¥ 
No. 12. This stone is rich in considerable crystals of augite to which it owes 
its porphyritic character, the felspar being very prominent, but much decom- 
posed. Crystals of quartz are very distinct in parts of the stone. The chlorite 
is less abundant and of a gray colour. It is to be remarked that in none of 
the diabese stones has mica been detected as an ingredient. 
No. 13 resembles No. 4, and is coarser in grain than No. 12. 
Nos. 14, 15, 16 and 18 call for no special observation ; they resemble 1 and 3. 
No. 20 is conspicuous for a yellow tint, which inspection by a lens shews to be 
due to a prominent ingredient mineral, which in its first aspect resembles 
olivine. Examined in the microscope this is seen to be augite which in this 
specimen of the rock is more varied in tint than in others, and somewhat 
smaller in the size of its crystals. In other respects this stone closely resembles 
that numbered 12, in which however the augite is browner. The felspar is 
more plentiful but is decomposed, containing a large amount of the flocculent 
gray chlorite which gives it a white aspect. Quartz is present only in very 
minute grains. The chlorite is a not inconspicuous ingredient and more green 
. than usual; while also the ilmenite or magnetite is somewhat more plentiful. 
No. 21. This stone is distinguished from some of the other diabase-stones 
before described by the augite crystals being less distinct than usual, being 
smaller and more regularly mingled with felspar, with which it forms a ground- 
mass, in which a few crystals of the mineral are seen with porphyritic promi- 
nence. The felspar crystals too are more completely filled with flocculent 
chloritic mineral and are nowhere so prominent as usual. In short the specimen 
is one of a less porphyritic variety of the diabase. Quartz can be recognized 
as in other cases, but is not plentiful. 
Nos, 22 and 23, closely resemble No. 21. = 
No. 24 is a small block much resembling No. 2, and externally presenting a 
somewhat yellow hue in its felspar. 
No. 25 also resembles No. 2, but the felspar is very opaque and white, and 
much decomposed. 
No. 26 is more .porphyritic than any of the stones last described and its 
felspar crystals are very white and metamorphosed. 
