42 Proceedings of Royal Society of Edinburgh. [sess. 
shall never forget my own surprise when I first went to examine a 
fresh section of this rock which was not parallel with the bedding, 
but across it, or perpendicular to it, and which being a well-protected 
surface in a very sheltered spot, showed at a little distance a 
perfectly smooth and homogeneous face of fracture. It was nearly 
as pure white as the finest loaf-sugar. Yet when I looked closely 
into it, I could distinctly see the parallel and perpendicular lines 
which indicated the rods, or little cylindrical columns which I had 
seen projecting on the weathered surfaces on the tops of the hills. 
Again, there are some other conditions in which these rods are 
especially conspicuous, and this is where the quartzite itself is not 
white, but more or less stained by the oxide of iron. Not far from 
the spot last referred to, I was living some years ago in a shooting 
lodge built near the foot of a precipitous line of crag which stretched 
straight up the hill behind the house. It was of a dull brown or 
chocolate colour, and, for a long time, it did not occur to me that 
this crag was an escarpment of the same quartzite, only differently 
coloured. On finding from its texture that it was so, I set to work to 
find the rods, and I very soon found a good many, which, to my sur- 
prise, were pure white — thus presenting a most conspicuous contrast 
with the surrounding rock. They were, however, not nearly so numer- 
ous, although of precisely the same form and character. For many 
years there was much doubt and speculation as to the nature and origin 
of these rods — whether they were some form of mineral concretion, 
or whether they were the marks and indications of some organism. 
Macculloch, in his well-known and admirable work on the Geology 
and Mineralogy of the Hebrides and adjacent Coasts, published in 
1819, devotes some pages to a careful and very accurate account of 
this quartzite rock, in connection with his account of the Island of 
Jura, and mentions almost all the principal places in Scotland 
w T here it appears, and where it maintains a substantial identity of 
mineral composition and of structure. The passage in which he 
alludes to the appearances now under discussion, is curious as 
showing how little he regarded them as at all characteristic, and 
how T little he thought them capable of any definite explanation. 
“ Occasionally,” he says, “also it (the quartz rock) contains those 
prolonged concretions and other well-known forms, which are 
common in the secondary sandstones, and which have been supposed 
