PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 59 
and chemical characters. Sooth to say, the first of these lend hardly any aid, 
if they do not even somewhat tend to confuse. 
As thus: Taking Dana as usual as our English guide, we find the following 
ranges of specific gravities 
from to 
Of Penninite ; = 0 all ; ; : ‘ (2°85 
Leuchtenbergite, . 2°61 : ey gl 
Ripidolite, . : . 26D)" ; Bee wits 
Chlorite, : : : : : : EG. ; 2°96 
Pyrosclerite, . : ‘ : : eure 
Epichlorite, . i ; i ar6 
Delessite, P : d P : ¢ ; : dH 42:89 
Strigovite, . ‘ : : : 2 : ‘ 2 . 37144 
Thuringite, . : : : ' : : «oO Lon 
to 
LOW 
From out of these, no one of which in their fine-grained or ill-defined forms 
can easily be distinguished from the others, only the two last can be selected 
as standing in any measure apart. 
But even as regards the three commoner species, I cannot say that the 
evidence of such specimens, as analysis indicates to me should be placed under 
each of these species, bears out the ranges of specific gravity as limited by 
Dana. 
In allocating them by constitution alone we have little difficulty as regards 
true chlorite. Its low content of silica, and to a certain extent its lower 
magnesia and water, and its high alumina and ferrous oxide, enable us clearly 
to draw the line between it and the others. 
But the larger amount of alumina in ripidolite is the sole feature of distinc- 
tion between that mineral and penninite. 
Allocating the varieties I have analysed in accordance with these lines, I 
find the specific gravities to have the following ranges :— 
' from to 
Of Penninite, . A pegs?) : ; : q A : : : 3° 099 
Ripidolite, . : f é ; f : 3 2° 823 ; 2° 959 
Chlorite, . : : : mei 09k. .. ; ' ; : odos 
Supposing my allocation to be correct, this shows that the three species do 
not differ in gravity. 
Searching for aid from geognostic relationships we find little or none, and 
are again brought painfully in face of one of the shortcomings of mineralogical 
works, a shortcoming which I have already alluded to in speaking of the 
VOL. XXIX. PART I. Q 
