THE MINERALOGY OF SCOTLAND. 429 
quantity of wires, of the thickness of needles, laid longitudinally together. The 
wires can be separated from one another with perfect ease. They pass trans- 
versely from side to side of the vein, which is about eight inches in width. 
Another vein is of the nature of a dense wad: it is about two inches in 
width, is devoid of structure, if it be not of a granular description, and it breaks 
with a well-marked conchoidal fracture. This, therefore, is probably Low’s 
“ flint-like mass.” 
There is one marked fact which is to be observed of all these veins; it is 
that at their sides, the yellow, loose-grained sandstone-rock is stained by the 
manganese, in a manner which forcibly conveys the impression that the ore did 
not exude from the rock into the vein-rent, but was poured into the rent, and 
then soaked to a small extent into the porous stone. The limit of the stain is a 
sharp line of demarcation ; it does not shade off with a fainter tinge to the 
smallest extent. 
Low, in his remarks upon this ore, says that it “looks as if it had been 
once in fusion, and had settled in a number of bubbles.” Though its usual 
occurrence, in fibrous mammillations after the manner of the hematites, by no 
means indicates such a mode of deposition, yet I have already had to allude to 
indications of its having been intruded into the veins from without ; and there 
are certain modes of its occurrence now to be described, which go a very long 
way indeed to show that some portion of it at least had been in a state of 
liquidity from heat. 
These modes of occurrence group themselves into four varieties. 
1. Drops which seem to have been sprinkled over a surface. 
2. Drops which seem to have fallen into narrow spaces, and to have moulded 
themselves to the bounding walls of those spaces. 
3. Pendulous masses which seem to have run down the surface of the sus- 
taining substance. 
4. Drops which exhibit shrinkage markings, and which, having fallen one 
upon another, have taken an impression or cast of the shrinkage markings 
of the underlying drop; and which drops are free from all attachments. 
In the case of the first three varieties, the so-called drops invariably lie 
upon the surface of the glossy limonite: in the case of the last they do not do 
so, but upon either the mammillated psilomelane, or upon other drops. 
In the first two cases the drops are perfectly spherical, except where in 
contact with their support, or where by juxtaposition they impinge upon each 
other. They vary in size from the smallest sparrow-hail, to bullets which would 
be about four to the pound. 
_ Their internal structure is obscurely fibrous. The pendulous masses have 
also an obscurely fibrous structure ; but the drops which come under head No. 
4 do not show any structure,—being like flint when broken. 
