THE SNOW 39 



are at length lost for months during the snowy 

 period. The snow is first built out from the banks 

 in bossy, over-curling drifts, compacting and ce 

 menting until the streams are spanned. They then 

 flow in the dark beneath a continuous covering 

 across the snowy zone, which is about thirty miles 

 wide. All the Sierra rivers and their tributaries in 

 these high regions are thus lost every winter, as if 

 another glacial period had come on. Not a drop 

 of running water is to be seen excepting at a few 

 points where large falls occur, though the rush and 

 rumble of the heavier currents may still be heard. 

 Toward spring, when the weather is warm during 

 the day and frosty at night, repeated thawing and 

 freezing and new layers of snow render the bridg 

 ing-masses dense and firm, so that one may safely 

 walk across the streams, or even lead a horse across 

 them without danger of falling through. In June 

 the thinnest parts of the winter ceiling, and those 

 most exposed to sunshine, begin to give way, form 

 ing dark, rugged-edged, pit-like sinks, at the bottom 

 of which the rushing water may be seen. At the 

 end of June only here and there may the moun 

 taineer find a secure snow-bridge. The most last 

 ing of the winter bridges, thawing from below as 

 well as from above, because of warm currents of air 

 passing through the tunnels, are strikingly arched 

 and sculptured; and by the occasional freezing of 

 the oozing, dripping water of the ceiling they be 

 come brightly and picturesquely icy. In some of 

 the reaches, where there is a free margin, we may 

 walk through them. Small skylights appearing here 

 and there, these tunnels are not very dark. The 



