110 Prof. Weiss on the different Systems of Crystallisation. 
drons. It might be called gewerdet-sechsgliedrig , or systema se~ 
nario-hemiedricum detortum , which will possess the remarkable 
property, that its solids will be turned sometimes to the right 
and sometimes to the left, as I have fully explained in a Me- 
moir on the Crystalline System of Quartz , which I have inserted 
among the Memoir es de la Societe des Amis Scrutateurs de la 
Nature de Berlin ; a property, besides, of which I have endea- 
voured to demonstrate the physical principle, in the way of its 
being polarised in the latera of the axes of this system, in the 
Memoirs of the Royal Academy of Berlin for 1817. 
But it is not Quartz alone which requires new subdivisions to 
distinguish it, in our fourth general case. Tourmaline presents 
another example, having some analogy with the tetarto-edral sys- 
tems of the other principal divisions. L shall not, however, de- 
tain you any longer on this subject. In making a comparison 
of my terms with those of M. Mohs, you will, I am persuaded, 
prefer mine to his, which appear to be too inconvenient to be 
substituted in their place ; particularly as mine were formed and 
published several years before those of M. Mohs. I confidently 
hope that you will find my method the most simple, and the 
most natural, of any that we possess ; and I may even go so far 
as to say with strictness, that, in many points, my method is not 
susceptible of farther simplification. I am, &c. 
Gottingen, ) Weiss. 
October 3. 1822. j 
Art. XIX . — On the Revolutions which have taken place in ike 
Animal Kingdom , as these are indicated by Geognosy. By 
Dr Fleming *. 
THE organic remains of the animal kingdom, found in the 
strata of this country, are generally supposed to bear a very close 
resemblance to the living races which inhabit the warmer regions 
of the earth, and to be unlike the modern productions of tem- 
perate and cold climates. In the firm belief of the truth of 
Abridged from his “ Philosophy of Zoology,” vol. ii. 
