TO Mv luQvy on the modes of Notation 
Swer, and from that to the Ladoga Canal. Across these great 
lakes, resembling seas in extent, the navigation is at times diffi- 
cult and dangerous. Storms and sudden gales of wind fre- 
quently occur, driving the vessels and timber-rafts from the 
sides into the middle of the lakes, out of sight of land, often 
proving destructive to them, and fatal to their crews. In order 
to prevent such accidents, Peter the Great set a-going the Lado- 
ga Canal ; and after its completion, the vessels which formerly 
navigated the lake were conducted along the Canal, protected 
from every risk. The rafts having passed along the Lado- 
ga Canal, enter the mouth of the River Neva, and the stream 
carries them down to Petersburgh. 
The timber when collected into the yards of the merchant, 
undergoes a farther preparation. Each tree is cut into a square 
form on the sides, or reduced to a log, so as to occupy as little 
room as possible on shipboard. When that o})eration is finish- 
ed, it is floated down to Cronstadt, where it is taken up by 
vessels appointed to receive it, and transported into other coun- 
tries. 
Art. VII . — On the modes Notation of JVeiss, Mohs, and 
Hatiy. By A. Levy, Esq. of the Academy of Paris, &c. 
Although the geometrical problems afforded by crystallogra- 
phy are all very simple, and may be solved by means of one or 
more plane or spherical triangles, yet it is convenient to have for- 
mulae for the cases which occur most frequently, giving imme- 
diately the values of the unknown quantities, in function of the 
data of observation. Some of these formulae I have had occa- 
sion to investigate, and I now submit them to you for insertion in 
your Journal, if you think any benefit may be derived from 
them. On this last point, I confess I have myself considerable 
doubt, because they have reference to the notation of Hauy, and 
because many other modes of expressing the relative position of 
secondary planes to those of the primitive, have lately been pro- 
posed, which, if generally adopted, would of course render my 
investigations comparatively of little use. It is true, that it does 
not appear to me that any of these new methods presents a 
^degree of simplicity, or any relations to theoretical views, which 
