30 
NATURE FOR ITS OWN SAKE 
Fog and 
smoke. 
Fog effects. 
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 froma 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 
