115 
On examining the charts already referred to it was seen that 
whenever the Helm occurred the sky was almost invariably cloudy 
to the eastward; and probably the stratum of cloud was of no 
great altitude. The distribution of pressure was mostly of a 
cyclonic character. 
The phenomenon appears to be due to the abrupt descent of 
the hills on the west, the air in pouring over the declivity is 
warmed in its descent and is consequently able to hold a greater 
amount of moisture in suspension. The cloud therefore is dis- 
solved on the western side of the Fell, and only re-forms at a 
distance of several miles after the disturbance caused by the 
irregularity in the contour of the land has been overcome. The 
Bar is produced by a rebound or ricochet of the air at the foot of 
the Fell, the Bar indicating the width of the upward current and 
also the point at which condensation takes place. ‘The roaring 
sound which is heard when the Helm Wind blows is no doubt 
_ due to the rush of cold air down the sides of the Fell. 
Similar winds occur on Table Mountain, Cape Colony, and on 
the Hackgalla Mountain in Ceylon. 
Sir John F. W. Herschel, in his A/eteorology, pp. 95-97, gives 
the following account of the “Table-cloth” :— 
‘*That the mere self-expansion of the ascending air is sufficient to cause pre- 
cipitation of some of its vapour, when abundant, is rendered matter of ocular 
demonstration in that very striking phenomenon so common at the Cape of 
- Good Hope, where the South or South-easterly wind which sweeps over the 
Southern Ocean, impinging on the long range of rocks which terminate in the 
FIG. 5. 
TABLE CLOTH 
CF CERCA 
NAS Na 
al Re ol fe es 
S: SS SA 
fa) 
ft X 
__ The “Table Cloth” on Table Mountain. Rough schematic diagram with 
vertical distances purposely exaggerated, modified from Herschel’s Meteorology. 
