The Helm Wind
|>||"Besides the permanent beauties of a country
diversified by hills and dales, mountains and lakes, there are transient subjects capable
of arresting the attention of the contemplative observer; amongst which are the mists or
fogs, forming over the surface of the lakes, floating along the sides of hills, or
collected into clouds hovering upon the summits of hills."
The Helm Wind is a most interesting and remarkable phænomenon, and it has called forth curiosity, and raised inquiry in the most careless observer, and many have been the conjectures as to its nature and cause. Dr. Barnes says - "The air or wind from the east ascends the gradual slope of the western1 side of the Penine2 Chain* or Cross Fell range of mountains, to the summit of Cross Fell, where it enters the helm or cap, and is cooled to a low temperature; it then rushes forcibly down the abrupt declivity of the western side of the mountain, into the valley beneath, in consequence of the valley being of a warmer temperature, and this constitutes the Helm Wind.
The sudden and violent rushing of the wind down the ravines and crevices of the mountains occasions the loud noise that is heard.
At a varying distance from the base of the mountain the helm wind is rarefied by the warmth of the low ground, and meets with the wind from the west, which resists its further course. The high temperature it has acquired in the valley, and the meeting of the contrary current, occasion it to rebound and ascend into the upper region of the atmosphere. When the air or wind has reached the height of the helm, it is again cooled to the low temperature of this cold region, and is consequently unable to support the same quantity of vapour it had in the valley; the water or moisture contained in the air, is therefore condensed by the cold, and forms the cloud called the Helm Bar. The meeting of the opposing currents beneath, where there are frequently strong gusts of wind from all quarters, and the sudden condensation of the air and moisture in the bar-cloud, give rise to its agitation or commotion, as if "struggling with contrary blasts." The bar is therefore not the cause of the limit of the helm wind, as is generally believed, but is the consequence of it. It is absurd to suppose that the bar, which is a light cloud, can impede or resist the helm wind, but if it even possessed a sufficient resisting power, it could have no influence on the wind which is blowing near the surface of the earth, and which might pass under the bar. #
The variable distance of the bar from the helm is owing to the changing situation of the opposing and conflicting currents, and the difference of the temperature of different parts of the low ground near the base of the mountain. When there is a break or opening in the bar, the wind is said to rush through with great violence, and to extend over the country. Here again, the effect is mistaken for the cause. In this case, the helm wind, which blows always from the east, has, in some place underneath the observed opening, overcome the resistance of the air, or of the wind from the west, and of course does not rebound and ascend into the higher regions to form the bar. The supply being cut off, a break or opening in that part of the bar necessarily takes place. When the temperature of the lower region has fallen and becomes nearly uniform with that of the mountain range, the helm wind ceases; the bar and the helm approach and join each other, and rain not unfrequently follows. When the helm wind has overcome all the resistance of the lower atmosphere, or of the opposing current from the west, and the temperature of the valley and of the mountain is more nearly equalized, there is no rebound or ascent of the wind, consequently the bar ceases to be formed, the one already existing is dissipated, and a general east wind prevails. There is little wind in the helm cloud, because the air is colder in it, than in the valley, and the moisture which the air contains is more condensed, and is deposited in the cloud upon the summit of the mountain. There is rarely a helm, helm wind, or bar during the summer, on account of the higher temperature of the summit of Cross-Fell range, and the upper regions of the atmosphere at that season of the year.
The different situations of the helm, on the side, on the summit, and above the mountain, will depend on the temperature of these places: when the summit of the mountain is not cold enough to condense the vapour, the helm is situated higher in a colder region, and will descend down the side of the mountains if the temperature be sufficiently low to produce that effect.
The sky is clear between the helm and bar, because the air below is warmer, and can support a greater quantity of vapour rising from the surface of the earth, and this vapour is driven forward by the helm wind, and ascends up in the rebound to the bar. In short, the helm is merely a cloud or cap upon the mountain, the cold air descends from the helm to the valley, and constitutes the helm wind, and when warmed and rarified in the valley, ascends and forms the bar.
An objection has been taken to this theory, an the ground that there is no helm wind in the valley of the Tyne3; but the circumstances are very different ; this valley is situated much higher than that of the Eden, and the summit of the mountain on the east, is considerably lower than the top of Cross Fell. The former valley has also a high bridge of mountains on the west, the latter a low and expansive plain. The fact that the helm wind never extends farther than the bar, tends to prove the truth of the theory. The following are Rev. John Watson's observations.
The places most subject to it are Milburn, Kirkland, Ousby, Melmerby, and Gamblesby. Sometimes when the atmosphere is quite settled, hardly a cloud to be seen, and not a breath of wind stirring, a small cloud appears on the summit, and extends itself to the north and south ; the helm is then said to be on, and in a few minutes the wind is blowing so violently as to break down trees, overthrow stacks, occasionally blow a person from his horse, or overturn a horse and cart. When the wind blows the helm seems violently agitated, and on ascending the fell and entering it, there is not much wind; sometimes a helm forms and goes off without a wind, and there are easterly winds without a helm. The open space is clear of clouds with the exception of small pieces breaking off now and then from the helm, and either disappearing or being driven rapidly over the bar; but through this open space is often seen a higher stratum of clouds quite at rest; within the space described the wind blows continually; it has been known to do so for nine days together, the bar advancing or receding to different distances. When heard or felt for the first time it does not seem so very extraordinary, but when heard and felt for days together, it gives a strong impression of sublimity. Its sound is peculiar, and when once known is easily distinguished from that of ordinary winds ; it cannot be heard more than three or four miles, but in the wind or near it, it has been compared to the noise made by the sea in a violent storm.
Its effect on the spirits is exhilarating, and it gives a buoyancy to the body. The country subject to it is very healthy, but it does great injury to vegetation by beating grain, grass, and leaves of trees, till quite black.
A similar phænomenon occurs at the Cape of Grood Hope; Professor Stavely had noticed one of the same kind near Belfast; and Professor Buche, when crossing the Alps, observed the like appearance on Mount Cenis, and one, called the Bora wind, occurs on the high ground near Trieste.
* From their Roman name, Alpes Penini.
# The open space between the helm and bar varies from eight or ten, to thirty or forty miles in length, and from half a mile to four or six miles in breadth; it is of an elliptical form, as the helm and bar are united at the ends. A representation of the helm, bar, and space between, may be made by opening the fore finger and thumb of each hand, and placing their tips to each other, the thumbs will then represent the helm on the top of the fell, the forefingers the bar, and the space between, the variable limits of the wind - Rev. J. Watson.
Mannix & Whellan, History, Gazetteer and Directory of Cumberland, 1847
1. Evidently this should read eastern.
2. sic - Pennine.
3. The Tyne rises in the Pennines, and flows eastward to the North Sea.
19 June 2015
© Steve Bulman