15 
Mr. Leipner accounted for this by supposing that cats killed more 
than they could eat. 
Mr. Carpenter thought that these might possibly be shrews, which 
were often killed by dogs and cats in mistake for mice. 
Mr. Henry K. Jordan, F.G.S., then read a paper upon Pseudomorphs. 
After some introductory observations, he said that all inorganic substances 
which crystallised— and but few were amorphous— crystallised in one 
or other of the six systems of crystallisation, the characteristics of which 
he pointed out ; as a rule the crystals were of one system only, when 
the substance was said to be monomorphous Several minerals, however, 
crystallised in two systems, or were dimorphous, as sulphide of iron, 
carbonate of lime, and others. 
The author thus continued — 
A Pseudomorph is a mineral which has not its own proper form, but a crystallo- 
graphic form belonging to another mineral. 
Thus we have Oxide of iron, which crystallizes in the Hexagonal system, in the 
form of Iron Pyrites, belonging to the Tesseral system. Again we have 
quartz, which belongs to the Hexagonal system, in the form of Fluor spar, 
which is a Tesseral mineral. These are Pseudomorphs. 
Pseudomorphs may be classed under five heads, namely — 
1st, Pseudomorphs by incrustation. 
2nd „ by replacement. 
3rd by loss of an ingredient. 
4th ,, by the gain of an ingredient. 
5th „ by exchange of ingredients. 
1st. A Pseudomorph by incrustation is formed when a mineral is deposited from 
a solution upon another pre-existing mineral, the form of which it assumes ; the 
original mineral sometimes remains, but very often decomposes, leaving an 
empty Pseudomorph. This class of Pseudomorphs can only be formed in the 
cavities of a lode or vein. 
2nd. Pseudomorphs by replacement are formed by a mineral being deposited 
from a solution, and filling up a cavity produced by the decomposition of a pre- 
existing crystal. 
3rd. Pseudomorphs by loss of an ingredient often occur, and are in most cases 
easily understood. Crystals of Sulphide of Iron, exposed to the atmosphere, or 
to oxygen, lose their sulphur by its oxidation— oxide of iron only remains. 
Oxide of Copper, by loss of its oxygen, is turned into metallic copper. 
A mineral called Heulandite, by the loss of its Alumina and Lime, becomes 
quartz. 
4th. Pseudomorphs by gain of an ingredient. I can illustrate this class of 
Pseudomorphs with the specimens of carbonate of copper after red oxide of 
copper. These crystals were formerly oxide of copper, the colour of rubies,, but 
carbonic acid having been generated by some mineral decomposition, and brought 
into contact with the crystals, chemically combined with them, and changed them 
