510 PROFESSOR HEDDLE ON THE RHOMBOHEDRAL CARBONATES. 
Steatite after 
6-51 
Serpentine after 
({MgO + 4H,0)SiO, + 4H,0 
Glauconite after 
{4FeO, $K,0)Si0O, + (4Fe,0,, +A1,0,) Si0,? + 3H,0 
466 + 2-3 — 35-5 = 7.88 
Prehnite after 
(2CaO, SiO, + Al,O,, Si0,) + H,O 
144 
413 + 2.87 > 6.86 
Prehnite after 
6-86 
Fassaite. 
(MgO, CaO, FeO)Sio, 
35 
116 +33-— =7 
Biotite. 
(£MgO, 4.1,0,)?, Si0,2 
320 + 2.9 - a 8.6 
Orthoclase, 
K,0, Si0,? + ALO; Si0,* 
218 
557 + 2-55 - an = 8-4 
Andesine. 
(CaO + N a,O) SiO, + ALO, ; $i0,° 
151 
402 + 2.67 aa e= 7-95 
Analcime, 
Na,O, SiO, + Al,O,, Si0,° + 2H,0 
196 
441 + 2.25 - => = 7.84 
In all the above cases the requirements of the law are fulfilled. 
It now behoves us to look for exceptions. 
The writer’s cabinet contains the following apparent exceptions:— 
Orthoclase after 
8.4 
or 
Albite. 
Na,O, SiO,? + Al,0,, Si0,? 
200 
525 + 2-62 ae = 77 
These three pseudomorphs occur along with others in the Kilpatrick hills; 

Laumonite. 
Ca0,SiO, + Al,0,Si0,3 + 4H,0 
205 
2 OS) — eee a 
AG = 2:3 3, = 6-61 
Heulandite. 
CaO, SiO,°, + Al,0,, Si0,° + 5H,0 
: 278 
609 + 2.19 — nO 6-95 
Stilbite. 
CaO, Si0,3 + Al,0,, SiO,? + 6H,O 
285 
6-27 + 2.2 — B- 6-63, 
‘ 
they are not hollow in the sense of having a central vacuity; they even have 

