THE MINERALOGY OF SCOTLAND. 431 
—each period having been of such a duration as sufficed for the solidification 
of each preceding drop. 
In these, a number, sometimes a large number, of Joose drops are superim- 
posed upon one another, without even so much adhesion as to allow the speci- 
men to be removed from the rock without their falling apart. 
There is here no limonite,—drop lies upon drop in immediate contact. 
The surface of each drop is highly polished ; but it is marked throughout 
with a number of projecting ridges, which bear the most perfect resemblance 
to a solidified crust that has been rent and roughened by the contraction of a 
shrinking and still liquid centre. 
Each drop has taken the most perfect cast of that which it has fallen upon 
(or at least of what it lies upon), both as regards the converging curvitures 
thereof, and the above-mentioned linear rugosities; and each drop is on ?zts 
upper surface lined and roughened in a perfectly similar way. 
If it be a large drop, it envelops several of those which are smaller and 
inferior, filling up every interstice between them; and the rugosities upon the 
upper surface of a large drop are ever larger and more boldly marked than 
those upon a small one; as might be expected from the contraction of a more 
ample mass. 
While such a structure as this is in every way accordant with igneous 
liquidity, it appears to be altogether inexplicable upon the theory of watery 
solution, or of deposition of particles which had been in suspension in a liquid; 
and the observant Mr. Low was fully justified in saying that it “looks as if it 
had been once in fusion, and had settled in a number of bubbles.” 
I may here state that I possess from another locality a specimen of perfectly 
amorphous psilomelane, which fills up all the interstices between a number of 
“stalactites” of hematite—and these stalactites have a markedly scorified 
appearance. 
But the question of the liquefiability of the mineral may be, to some extent, 
determined by actual experiment. 
In ascertaining the amount of the water in the two manganesian minerals 
which occur here, it was found that after the application of the heat—nearly a 
white heat—obtainable from a three-jet Griffin blast furnace, the crushed powder 
of the psilomelane had agglutinated throughout; while the portion thereof which 
was in contact with the sides and bottom of the crucible, had fused so far as 
to be firmly adherent thereto, and to have become glistening in lustre. 
The fine powder of the wad, again (which differed from that of the psilome-. 
lane in its comportment under heat, in this, that it became brown at a red heat, 
while the colour of the psilomelane was unchanged), was not only fused to the 
crucible in its lower portions, under the influence of the white heat, but had 
collected into distinct drops, which were more or less rounded. 
