135 
The White Moss Loch. 
Geology, Climate and Rainfall of the District. 
The loch lies in a natural depression 0'75 mile (c. 1,200 m.) to 
the north of the Ochil Hills. This depression occurs at the end of 
a branch from a secondary valley which runs along the foot of the 
hills. At its nearest point the river Earn, which finds its course 
through the main valley of the Strath, is 1*25 mile (c. 2,000 m.) north 
of the loch. From present conditions it is difficult to say whether 
a stream of any size ever followed the valley in which the loch is 
situated. If so, the direction would be from west to north-east, but 
at present the valley to the north-east becomes constricted and only 
a ditch leading from the loch occupies its bottom. As has happened 
in other parts of the country it is probable that cultivation of the 
surrounding land has considerably altered the physiographic features. 
Although so near the Ochils, the loch is not associated with 
the andesitic lavas of these hills, but rests on the Old Red Sandstone 
at an elevation of 175 feet (c. 53 m.) above sea level. Mud consist¬ 
ing of fine particles of sand mixed with much organic material 
covers the bottom to a depth of at least two metres. There is no 
inflow stream, but a ditch at the west end conducts into the loch a 
considerable amount of surface drainage during the winter months. 
The surrounding fields slope towards the loch which thus receives 
most of their drainage. There are several springs in the vicinity 
and these may help to maintain a supply of water. The outlet at 
the north-east corner is also artificial and only during winter does 
water escape in any quantity. From the rapid deposition of organic 
material at the bottom it is evident that at one time the loch was 
deeper than it is now. At present the water is nowhere more than 
a metre deep during the summer months, although in winter the 
depth may be almost twice this. The bottom is the shape of a 
shallow saucer, and if all the water could be drained off, a 
comparatively flat expanse of loose organic mud would remain. 
The following data regarding rainfall and temperatures for the 
district have been obtained from observations taken over the past 
twelve years. 
The average annual rainfall is 38-5 inches (c. 980 mm.). The 
winter months are the wettest, and thus the water level is highest 
when the temperature is lowest. The average of the mean daily 
temperatures is 46°F. (7*7 n C.). In 1911, 87‘2°F. (30 , 6°C.) was 
recorded as the maximum for the year and for the period during 
which observations have been made. The average of yearly absolute 
niaximum temperatures is only 73°F. (22-7°C.). The absolute 
