135 
of Weiss , Mohs , and Haiiy. 
Fig. 6. be considered as deriving from a rhomboid, the superior 
edges of which should correspond to the lines da,dc , &c., by a de- 
crement on its superior edges, the law of that decrement would be 
y - .. gr /JQ - 
expressed by^ 4 - 1 =• . It is equally evident that 
r J x — y x — y j 
the same dodecaedron may be considered as the result of a de- 
crement by 
x 
rows 
in breadth on the superior edges of the 
y — * 
rhomboid, whose superior edges should correspond to the lines 
a 6, a d> &c. ; or again, by ^ rows in breadth on the 
y — z 
lateral angles of the rhomboid, the oblique diagonals of which 
cTimilrl rl linoci /I n /I n Xr/-» • rw ^ I . 
* " X — y 
rows in breadth on the lateral angles of the rhomboid, the ob- 
lique diagonals of which should correspond to the lines a b, adi 
'll — * ££ 
nr, lastly, by rows in breadth on the inferior edges of 
x — y 
the rhomboid, the inferior edges of which should correspond to 
the lines a b, b c, c d of the dodecaedron. And since x, «/, z are 
found to be generally simple numbers, it is clear from the expres- 
sion we have j ust found for the laws of decrements on the hypo- 
thetical primitive forms, that they will also generally be very 
simple. 
( To be continued .) 
Art. XXII.' — On the Preservation of Zoological Specimens 
from the Depredations of Insects. By Thomas S. Trail, 
M. D. F. B. S. E., &c. * Communicated by the Author. 
The difficulty of preserving zoological specimens from the 
depredations of insects, is a subject of regret and anxiety to 
* The method of preserving zoological specimens recommended by Dr Traill, 
we have been in the practice of employing to great extent, and most successfully, in 
the Museum of the University, for a considerable time past.— E d. 
