47 
everywhere by a mantle of black, sodden, spongy peat, whence, at 
most seasons of the year, moisture oozes out and saturates every- 
thing within reach. It is only along a crag, or at the bottoms of 
a few valleys that drier conditions prevail. 
This marked difference in the physiography of the regions at the 
back of the fell and along its face, or on either side of the Escarp- 
ment, is intimately connected with the factors concerned in the 
generation of the Helm Wind. What happens I conceive to be 
this. A light breeze blowing from east to west strikes the shores 
of Durham and travels inland. Where the wind traverses the 
ay 
warmer and drier lowlands bordering the coast its temperature is 
slightly raised, and its density diminished in proportion. Travelling 
inland, it encounters, on the west side of a north and south line 
through Bishop Auckland, the commencement.of the slope whose 
westward continuation forms the moory uplands just referred to. 
Here the wind passes across a surface that is perennially moist, 
and, as it travels inland, it traverses for a distance of nearly thirty 
miles in a direct line, a surface wrapped in wet peat, whose 
‘moisture is in a condition the most favourable possible for rapid 
evaporation. Millions of tons of water must be withdrawn from 
_the wet peat daily by the action of the wind alone. As a result of 
this process of evaporation the temperature of the air becomes 
_ lower and lower by this cause, as it travels nearer to the Escarp- 
ment. With the lowering of the temperature the density of the 
air is increased, and reaches its maximum density where the 
culminating ridge is attained. Another factor may contribute to 
the same result, namely, the heaping up of the air driven from the 
sea level up a slope to an elevation of between two thousand and 
, ree thousand feet above the sea. Mr. William Atkinson of 
Knock considers that this is the most important factor of all in 
‘the generation of the Helm Wind. Be either factor the more 
important, or be both equally concerned, it is quite certain that 
the denser mass of air moving westward presently reaches the edge 
of the Escarpment, where, as we have seen, the surface rapidly 
alls to a level lower by nearly two thousand feet. It is along this 
zone that we meet with the thick stratum of warmer and lighter 
