THE CANADIAN NATURALIST. 



C. — What is the cause of these crystals called hoar frost ? 

 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 earth, 

 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 

 (FringiUa 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 



