Such flowers are of many shapes, but more generally they have six petals each. If a ray of sunlight is thrown upon a slab of ice, through a lens, so as to concentrate the heat, then, as the ice melts, the sparkling of these tiny florets can be seen; and when their magnified image is cast upon a sheet, the six-petalled flowers become clearly visible. Even more beautiful than the ice-flowers embedded in solid ice are the ice-flowers embedded in snow. They too are made of tiny spicules or needles of ice; and they too, while varying much in shape, are commonly six-petalled. Solid blocks of ice are at first sight so unlike masses of feathery snow that a child would be surprised to hear a snowflake spoken of as “ice.” Yet the difference between the two lies mainly in the arrangement of the little ice-needles, in the way they are put together. Those of hard ice are more densely packed; those of snow are more loosely joined, with open spaces between, full of air. It is the abundance of air, mixed in with ice-needles, catching and reflecting light, which gives to snow its whiteness. In some cases, however, as with glacier-ice, the texture is so close--like that of glass--that neither flowers nor needles are discernible. The fact that snow may be, through hard pressure, actually transformed into firm ice--and this is an everyday occurrence in the high Alps--shows how closely akin the two are. Every country in the world has, at a certain height, that which is called “the line of perpetual snow,” or, more briefly, “the snow-line.” Below that limit snow may fall in winter, and water may freeze, but both vanish in the summer. Above that limit snow and ice are found all the year round, lessening to some extent in summer months, but never disappearing. Over the equator the snow-line is about sixteen thousand feet high, or higher than Mont Blanc; so if Mont Blanc were situated on the equator it would not be a snow-clad mountain. At the north and south poles the snow-line is down at the sea-level. Summer warmth there does not suffice to get rid of winter ice and snow. Between the equator and the poles the snow-line varies in each country, according to that country’s position and climate. Above the snow-line on lofty Swiss mountains heavy falls add perpetually to the mass of snow. During the summer a certain degree of thawing goes on, but never anything like enough to balance the wintry additions. Exactly at the snow-line the quantity of snow which falls and the quantity which thaws in the year are about equal. Lower down the yearly thawing exceeds the yearly snowfall. But if, above that line, more snow is being added year by year than can thaw and flow away, must it not be that those mountains which wear perpetual snow are always growing higher?