30 



NATURE FOR ITS OWN SAKE 



Fog and 



smoke. 



Fog tffecU. 



peared entirely. Of course the deepening and 

 the thickening of the fog-bank enfeeble and 

 gray the light. When combined with dust 

 and smoke, as in large cities, it is sometimes 

 dense enough to require the lighting of street 

 lamps in the middle of the day. How it ob- 

 scures the vision everyone knows who has been 

 in London at such times, or has crossed on the 

 New York ferry-boats, with the pilots picking 

 their way by the sound of whistles and bells. 

 In such fogs a few feet are often sufficient to 

 efface objects entirely. 



In the country a fog never appears to be so 

 thick as in the city, though in low marsh places 

 it banks up and obscures land and water 

 very effectually. Seen from a high place look- 

 ing down, the shore-fog is not unlike a cloud 

 below one in an Alpine valley ; and with the 

 sunlight beating upon it the fleecy spun-silver 

 effect is just as beautiful on the one as on the 

 other. There is no limit to the fantastic forms 

 a fog will assume when seen from a height. At 

 times when the dark tree-tops protrude above it 

 the appearance is that of a landscape buried in 

 snow, at other times the meadows seem flooded 

 with milk-white water, or suffocated with drifts 

 and currents of smoke. The small islands off 



