










228 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
So far as the power of the lens went, the pores seemed similar to those 
of hypersthene (Paulite). 
The structure, therefore, is identical with 
that under consideration, only that in Murchi- 
sonite it is porous, or empty. 
A crystal lent me by Professor Nico. 
actually showed this identity. This crystal 
was a hemitrope of the form depicted; it 
was got in a quarry at Upper Craigton, Hil 
of Fare, Aberdeenshire. 
Biot Mere oun ye. The general colour of this hemitrope is a 
reddish brown ; the faces 6, which are smooth and somewhat transparent, show 
the fibrous structure shining up from the depths, on account of the relative 
lightness of its colour. The face ¢ again shows a lineation through deficiency 
of substance ; consisting of a transverse series of pitted markings, which are the 
openings of the pores. 
A. point of considerable interest in this crystal is that the portion covered by 
the face m is either of a purer, or of a different nature from that of the general 
mass. It forms a small wedge of nearly colourless and transparent material det 
in to the general substance. 
The weight of this crystal in air was 48°28 grains ; in water, 27°12. 

48°28 —27°12=21°16, 
48°28+21°16= 2°282, 
being the specific gravity with pores air-jilled. 
Boiled in water, air escaped from the pitted markings ; after cooling in water 
and drying it weighed 50°13 grains in air, and 29°13 in water. 
48 °28—29-13=19°15, 
48°28 +19°15= 2°521, 
which is thus the true specific gravity. 
But the water weight of the pores is equal to the difference between 48 :28,— 
its weight with these pores air-filled, and 50°13,—its weight with pores water- 
filled =1-85. ; 
And 1°85 x 2°521=4-66,—the weight of the bulk of the pores if they 
were solid. 
This 4°66 added to the original weight of the crystal, 48°28, gives 52°94 
as what would have been the weight of the crystal if it had been solid; ant 
52°94+4-66 gives 11°36. 
