244 Captain J. D. Cunningham on the Limits of 
heat, which melts the snow ; while, on the northern face, the 
slopes merge into the swampy flats of Toorkistan, scarce 
500 feet above the sea, and are thus met bya cold atmo- 
sphere, down to a low level, in the aid of the coldness due to a 
northern aspect. _ 
Relative heights on extreme edges of mountain-belts—It will 
indeed be found, that in any broad mountain-chain resting on 
a plane inclined to the sea-level, and running nearly east and 
west, the effect of latitude on temperature may be discarded, 
and that elevation above the particular country, and not above 
the general ocean, is mainly, although not solely, to be con- 
sidered in determining the limits of perpetual snow on the 
two edges of the belt. The line of snow will rise as the plane 
of the country rises, and keep above it at a continually de- 
creasing distance, until the diminishing temperature due to 
increasing height, causes the two to coincide, a phenomenon 
which of course cannot occur in the temperate zones, as we 
know of no table-land so high as to be always frozen on the 
surface. 
Relative heights on opposite sides of the same single hill of 
a chain.—This reasoning does not, however, apply to the 
limits of snow on the northern and southern slopes of any 
one hill or mountain of a broad and complex chain ; and as a 
rule, the snow will be found to lie lower on the northern than 
on the southern face of a single peak. In such an instance, 
neither difference of latitude nor inclination of plane can or- 
dinarily have any effect, and the only element to be taken 
into consideration is the direct play of the sun’s rays, which, 
in the northern hemisphere have most power on a hill-side 
looking to the south. Captain Hutton, in his papers in Dr 
M‘Lelland’s Journal of Natural History, had such isolated 
hills in view when he asserted that the southern limit of snow 
was higher than the northern one, and when he sought the 
support of my experience on the subject, as I was then, te 
moving about in Ludakh and Kunawur. 
Dibiange iis of illustrative sketch.— The accompanying sketch 
represents what | believe to be the true state of the case 
with regard to the Himalayas, whether a line be drawn north 
and south across them, between the Gogra and Ganges, or 
