314 MR. H. H. W. PEARSON ON THE 
very different. As will be seen later, the rainfall above 5000 feet 
is comparatively large and uniformly distributed throughout the 
year. The air is always highly charged with moisture, and 
above 5000 feet dense fogs are very frequent and lasting *. 
Occasionally, at 6000 feet and upwards, the temperature sinks 
below 0° C., and a little hoar-frost is formed on the grass before 
sunrise. 
Under these conditions, soil and humus accumulate to con- 
siderable depths at the tops of the hills and in the valleys, and to a 
less extent upon the slopes. In hollows from which the drainage 
does not readily eseape, swamps are produced in which a con- 
siderable formation of humus, formed chiefly of the parts of 
species of Sphagnum, Eriocaulon, Cyperacex, and Graminex, may 
accumulate. 
The term “ patana,” then, includes two very different forma- 
tions, which can be almost separated by the 4500-feet line. 
Below this elevation we have a dry area, whose climatic conditions 
are comparable to those of an American savannah ; above 4500 
feet the climate and the soil alike have considerable resemblances 
to those of a European moor which in favourable localities 
becomes marshy. 
Origin of the Patanas. 
The arguments in favour of attributing the origin of the 
patanas to the combined effects of the climate and the periodic 
grass-fires must now be considered, 
lf we imagine the patana-fires, and other causes which may 
be active in extending the patanas westwards to cease, and 
a consequent re-afforestation of the western patanas to com- 
mence—and experience shows that it does commence under 
such circumstances—the new forest-growth would reach in time 
an eastern limit, below and beyond which it would not extend. 
As the forest advanced it would increase the precipitation of 
* During three days (Aug. 9, 10, & 11) spent on Horton Plains (7000 feet), 
the atmosphere was not clear for half an hour, and for the greater part of the 
time we were enveloped in a dense mist, This is a common experience of 
visitors to Horton Plains. 
Nuwara Eliya (6200 feet), so well known as a Sanatorium, is as constantly 
saturated with dense fogs as with its notoriously heavy rains. A well- 
known writer speaks of “the endless procession of grey clouds out of doors, 
as they come rolling down from the gloomy black forests on the dingy dank 
moor (i.e. patana), and the shuddering surface of the icy lake” (Haeckel, 
“A Visit to Ceylon,’ trans. by Clara Bell, London, 1883, p. 289). 
