356 On Rain, Evaporation, Se. 
Dorsetshire, Devonshire, Cornwall, and Somer- 
setshire, from the Medway to the lower Avon 
inclusively, in an extent of 11.000 square miles, 
do not present us with many large rivers. From 
their number and magnitude, we cannot form a 
high estimate of their produce. The quantity of 
rain for those counties is indeed near the aver- 
age for the kingdom, as far as the preceding 
observations determine; but the milder tem- 
perature of their winters and greater heat of their 
springs and summers, will cause a greater eva- 
poration thah in some other parts: It is pro- 
bable the rivers in these counties may amount, 
when taken together, to 14 times the magnitude 
of the Thames. The rivers that disembogue 
their waters on the coast of Lincolnshire, Nore 
folk, Suffolk and Essex, from the Humber to 
the Thames, though drawn ftom a country of 
7000 square miles, manifestly fall far short of the 
Thames, The two places in this district, for 
which we have accounts of the rain, Norwich 
and Upminster, give a mean of only 22+ inches 
annually. . This, with the flatness of the country, 
which prevents the water from. running off in 
some degree, makes the rivers much less than 
what might otherwise be expected from the ex- 
tent of ground. ‘Thete are but 3 or 4 of any 
consequence. Probably all the rivers may 
amount to half the size of the Thames, There 
a ae 
