332 
THE CANADIAN NATURALIST. 
C. — What is the cause of these crystals called hoarfrost ? 
or^ rather, in what manner are they produced ? 
F, — They are never found except after those nights in 
which the floating vapours are condensed and precipitated in 
the form of dew : a cold stratum of air resting on the earthy 
freezes the minute drops as they are deposited, and they 
shoot into these slender crystals. Hoar frost is frozen dew : 
its delicacy is owing to the minuteness of the drops. 
C. — Here is the skeleton of a maple leaf, which has been 
macerated in water till the substance has been dissolved, 
leaving nothing but the veins. What a labyrinth of net - 
work is here ! 
F, — The veins or nervures of leaves are not put out at 
random, but ramify in a perfectly regular arrangement, differ- 
ing very widely in different plants. This mode of arrange- 
ment is important, as upon it the form of the leaf depends. 
In the maple, you see several main veins running from the 
junction of the leaf with the foot-stalk, and proceeding to the 
points or lobes of the leaf ; these send out smaller side-veins, 
and these finer still, till such an immense number of ramifi- 
cations is produced as we here see. When perfect, the inter- 
stices were filled with a cellular green substance, called pa- 
renchyma^ enclosed between two transparent skins. But all 
this has disappeared, and left only the framework, a specimen 
of lace of nature's own manufacture. 
C. — The Robin ( Turdus Migratorius ), the Snow-bird 
(Fringilla Nivalis), and the Sparrows, (F. Melodia, &c.) 
appear to have retired to the south : they were to be seen 
almost every day, up to about a week ago, but since that 
time I have not seen them. 
F, — There is much more difficulty in observing the de- 
parture of migratory birds than their arrival : as the first 
