16 OE Dutton—ffect of a warmer Climate upon Glaciers. 
ane: hotter than any ever known before, and add their 
potency to the annual liquefaction. A period of snowfall in 
midwinter has yes once without compensation ; a period of 
melting heat in midsummer has made its appearance as a clear 
gain to the _ Eauehaeton, This is the net result of the 
warmer climat 
31.) Let us Vexandind this a little more in detail, taking a 
special case by way of illustration. Let us consider the climate 
of a region situated in rather high latitudes, say in the neigh- 
borhood of 50° to 55°, where the present mean temperature of 
precipitation touches zero on the 10th of October. For three 
or four weeks before and after that date the storms will some- 
times yield rain, sometimes snow—the rain at first being more 
and then less and less frequent until notbing but snow falls. 
Similarly in the spring (April 15th?) there is a date at which 
the mean temperature of precipitation rises up to the zero line 
and passes above it with a period on either side in which snow 
and rain alternate—the snowfall gradually vanishing. hoa 
we have four seasons, one of summer rainfall, one of winte 
snowfall, and two seasons (autumnal and vernal), where the 
rains and snows are dove-tailed with each other. It is also 
necessary to remember that we are now considering an average 
year as before described, and we must stop a moment to con 
sider the elements of which that year is made up. Every call 
endar date has a certain time, rate, temperature, and amount, of 
precipitation which is found. by averaging the supposed obser: 
vations of precipitation occurring on that date for hundreds of 
duration siterdasiins with as many short dry intervals. 
Suppose now a warmer climate supervenes with a heat incre- 
ment sufficient to postpone the time at which the mean tem- 
perature of precipitation touches zero until the 15th of Novem- 
ber. In that case the 15th of November takes the precipitation 
which now pertains to October 15th, subject to a qualification 
which will be ee speedily. November 20th takes the 
precipitation of October 20th and soon. Thus the winter is 
driven forward in seu. On the other hand the spring comes 
earlier; and, in inverse order, the winter is driven backward. 
The former may be called the procession of snowfall, the latter 
the recession of snowfall. In mid-winter the procession and 
recession meet and crowd out entirely a certain period of time 
in which snowfall formerly occurred. But the rate of precipi- 
tation during mid-winter has increased because the temperature 
is now higher at which ie ues takes place. But this 
