Even on the shadow-side of the Valley the frost is never very sharp.

The lowest temperature I ever observed during four winters was 7 degrees Fahrenheit.

The first twenty-four days of January had an average temperature at 9 A.M.of 32 degrees, minimum 22 degrees; at 3 P.M.the average was 40 degrees 30', the minimum 32 degrees.

Along the top of the walls, 7000 and 8000 feet high, the temperature was, of course, much lower.

But the difference in temperature between the north and south sides is due not so much to the winter sunshine as to the heat of the preceding summer, stored up in the rocks, which rapidly melts the snow in contact with them.