474 



PHYSICAL GEOGRAPHY. 



Ireland 



Holland 



Switzerland 



Fiance 



Germany 

 Italy 



Dublin - 



Limerick - 



Hague 



Utrecht - 



Ley den - 



Zurich - 



Geneva - 



St. Bernard 



Paris 



Lisle 



Metz 



Caen 



Lyons 



Grenoble - 



Montpelier 



Rennes - 



Limoges - 



Evreux 



Berlin - 



Wurtemberg 



Rome 



Naples 



Venice 



Milan 



Padua 



Inches. 



22-2 



35 



28'4 



28-74 



31-49 



33-85 



51-18 



63-13 



21-26 



29-92 



26-37 



21-65 



:J3-07 



34-25 



29-92 



22-44 



29-16 



21-65 



20-6 



17-71 



21-26 



37-40 



31-89 



37 



39-76 



Inches. 



Pisa - - 48-82 



Genoa- - 55 -11 



Tolmezzo (Fiiuli) - 86 -6 1 

 Confugnana (Apennines) 97 '24 



Spain Carsagnana - - 9807 



East Indies Bombay - 78-1 



Calcutta - 72 



Benares - 46 



Tellichery - - 1 16 



Arracan - 200 



Delta of Indus - 20 



West Indies St. Domingo - - 120 



Grenada - - ] 12 



United States Charleston - 54 



Cincinnati - - 36 



Frankfort, Kentucky - 54 

 Williamsburg - 47 



Cambridge - - 47 



Rutland, Vermont - 41 



Brunswick - - 40 



Philadelphia - - 30 



Brazil Maranhao ' - - 280| 



Venezuela Cumana - - 8 



Africa Algiers - - 29*2 



A considerable portion of aqueous vapour in the atmosphere is frozen in the cold season 

 in extra-tropical latitudes, and the particles of ice uniting together in their descent become 

 converted into flakes of snow, and cover the surface of the earth with a mantle of the 

 purest white, stretching over bush and brake, lawn and mountain. Snow, examined with 

 the aid of a microscope, exhibits structures of exquisite beauty, regularity, and endless 

 variety, though it sometimes presents no peculiarity of form, but falls in very minute 

 globular particles. Commonly a snow-flake consists of a series of crystals formed inde- 

 pendently in the upper regions of the air. These are united in groups while descending 

 through the atmosphere, by its agitations striking them against each other. The flicker- 

 ing and gradual descent of the flakes is owing to their great extent of surface in comparison 

 with their volume. A number of brilliant icy spiculse, or points diverging from a common 

 centre, resembling stars having so many rays, apparently wrought with the nicest art, is 

 the usual form of the crystals, which are for the most part hexagonal, presenting a nucleus 

 with six divergences. This stelliform shape is the ordinary appearance of snow, but the 

 detail varies, as in the adjoining illustration. Dr. E. D. Clarke, speaking of the breaking 

 up of the winter season at St. Petersburg, remarks: "Snow, in the most regular and 

 beautiful crystals, fell gently on our clothes, and on the sledge, as we were driving through 

 the streets; all of them possessed exactly the same figure, and the same dimensions. 

 Every particle consisted of a wheel or star, with six equal rays, bounded by circum- 

 ferences of equal diameters ; they had all of them the same number of rays branching 

 from a common centre. The size of each of these little stars was equal to the circle 

 presented by dividing a pea into two equal parts. This appearance continued during 

 three hours, in which time no other snow fell, and there was sufficient leisure to examine 

 them with the strictest attention." A microscope applied to a flake of snow will unfold 

 this mode of structure, as well as other varieties in our climate; but it is in the polar 

 regions that snow assumes its most beautiful and varied forms. Scoresby has figured 

 ninety-six varieties, distributed into classes of lamellar, spicular, and pyramidal crystals, 



