336 



NA TURE 



\. lugust 7, 1S84 



erful acids. P. n, column 1, line 34, " i860" 

 should be " 1680" ; p. 12, column 2, line 28, and als 1 p. 1 -;. 

 column 1, line 5, steatite should lie pitchitom (a vitreous variation 

 of pyroxene andesite). R. 1 >. M. Verbeok, 



Director of Java Geological Survey 

 Buitenzorg, Java, June 19 



THE METEOROLOG\ OF BEN NEVIS 



AS regards changes of weather and many other pro- 

 blems of meteorology, a knowledge of the vertical 

 variations which take place in the atmospherical con- 

 ditions is of first importance : and the only way we can 

 hope to arrive at this knowledge is by regular observa- 

 tions made at stations as near each other as possible in 

 horizontal direction, but differing as much as possible in 

 height. This point was very clearly seen many years ago 

 by the late Mr. Allan Broun, and the idea was practically 

 worked out by him in the elaborate series of meteorologi- 

 cal and magnetical observations simultaneously made on 

 the peaks and ridges and in the adjoining valleys of the 

 Western Ghats. These observations are the best any- 

 where yet made to supply the observational data for the 

 discussion of some of the more important problems of 

 meteorology; and the science sustained no ordinal \ loss 

 in the death of Mr. Broun before he had discussed the 

 observations which had been collected by his genius, 

 energy, and self-denial. 



Xext in scientific value to Mr. Broun's observations are 

 those made on Ben Nevis since June 1881. The special ad- 

 vantages of Ben Nevis as a meteorological observatory are 

 that it rises to a height of 4406 feet, and is little more 

 than four miles distant from the sea at Fort William, and 

 that it is situated in the track of the great storms which 

 sweep over North-Western Europe from the Atlantic. 

 Hence observations made on the top and at the base of 

 Ben Nevis possess a value altogether unique in meteor- 

 ology ; particularly in discussing the atmospheric move- 

 ments which accompany cyclones and anticyclones, and in 

 itigating tornadoes and other destructive winds which 

 originate when the air is abnormally warm and moist 

 near the surface, while aloft the temperature and humidity 

 diminish with abnormal rapidity. 



For the preliminary inquiry which is necessary in order 

 to determine the chief points in the meteorology of Ben 

 Nevis, there are now available for a comparison of the 

 climate of the top of the mountain with that of the sea- 

 level at Fort William, simultaneous observations for 

 twenty-two months, viz. : from June to October of the 

 years 1881 and 1S82, and from June 1883 to June 1884. 

 As regards the temperature, the monthly means for Fort 

 William were compared with the normal monthly temper- 

 atures of that place as given in the paper on the "Climate of 

 the British I -lands " {%ourn. A', ott. Met. Soc, vol. vi. p. 33). 

 From the differences thus obtained, the approximate nor- 

 mal temperatures at Ben Nevis Observatory were deter- 

 mined. The coldest month is February, the mean being 

 22 o, and the warmest, July, 41 J '3, August being nearl) 

 as warm, the mean being 411 : and the annual mean tem- 

 perature 30°'9. Comparing the normals with those of 

 Fort William, the greatest difference is iS Q '0 in May, 

 from which it steadily diminishes to I4 r '9 in December, 

 and then rises more rapidly to the maximum in May ; the 

 annual difference is i6°'3. The greatest difference, or the 

 most rapid fall of temperature with height, is in the spring 

 and early summer, when the climate of the west is driest, 

 the temperature of the Atlantic lowest relatively to that 

 of the air, and the top of the mountain still covered with 

 snow. The least difference is in late autumn and early 

 winter, when the climate of the west is wettest, Ben Nevis 

 quently and densely clouded, and the temperature 

 of the Atlantic highest relatively to that of the air. The 

 observations of temperature at the high- and low-level 

 show a variation with the hour of ^the day even 



more decidedly marked than that with season. Thus, in 

 January the decrease of temperature, deduced from the 

 mean maxima and minima respectively were i6 D '2 and 

 l5°-2, but in April these were 23° - l and i2 0- 9, being thus 

 in January nearly ecjual, whereas in April the difference 

 of the maxima was nearly double that of the minima. 



The annual means give, therefore, a decrease of tem- 

 perature with height at the rate of i° for every 270 feet 

 of ascent— the most rapid decrease being 1° for every 

 245 feet in April, and the least rapid 296 feet in De- 

 cember. 



But the individual observations show wide divergences 

 from these rates of decrease. As disturbing conditions, 

 the more important of these are the instances of ab- 

 normally large decrease, seeing that these imply a tem- 

 perature near the surface much above the normal with 

 respect to the higher strata, by which the equilibrium of 

 the atmosphere is destroyed, and rapidly ascending and 

 descending currents are generated, thus giving rise to 

 some of the most destructive storms of wind. Of the 

 illustrations the observations give of a rapid decrease, 

 reference may be made to those of October 13, the day 

 preceding the great storm which proved so destructive to 

 the fishermen on the Berwickshire coast. 



Even more striking, and, as regards their bearing on the 

 theory of storms and weather changes, perhaps even more 

 important, are those instances of abnormally small differ- 

 ences between the temperature at the top and base of the 

 mountain, of which a good example which occurred on 

 September 21, 1SS2, was given in NATURE, vol. xxvii. 

 p. 176. All such cases have been accompanied with a 

 high temperature and an excessive dryness of the air. It 

 is these qualities of air which immediately connect the 

 phenomena with the great cyclonic and anticyclonic 

 systems in which or near to which Ben Nevis is for the 

 time situated. The most striking case of all occurred on 

 December 31, 18S3, on which day the maximum tempera- 

 ture at Fort William was 3o°"6, and minimum 27' J '2, these 

 being at Ben Nevis Observatory 32°x> and 22°'8. At 

 II a.m. the temperature at Fort William was 27°'5, but 

 on Ben Nevis it was 32°'o, with a wet bulb as low as 

 24 3 '4. Hence at this hour the temperature of the air was 

 4''5 higher at the Ben Nevis Observatory than at Fort 

 William, 4406 feet lower down, and this relatively high 

 temperature was accompanied with excessive dryness 

 represented by the humidity of 33. From 6 a.m. to noon 

 temperature was continuously higher on Ben Nevis than 

 at Fort William. At 1 1 a.m. the abnormality in the 

 vertical distribution of the temperature amounted to 20°'5. 

 It is of importance to note that at this time of relatively 

 high temperature and great drought, atmospheric pressure 

 was \ery high at the Observatory, the reading of the 

 barometer at 32 being 23915 inches, being absolutely the 

 highest that has occurred from November 28, 1S83, to 

 June 30, 1884. At Fort William the sea-level pressure 

 was 3060S inches. 



Another peculiarity of the temperature is the small 

 diurnal variation caused by the sun at all seasons, but 

 particularly in winter ; and the large variation due to the 

 temperature changes w-hich accompany the passage of 

 cyclones and anticyclones over the Observatory. The 

 means of the hourly observations show that even in May the 

 difference between the mean warmest and mean coldest 

 hour was only 3°'3- In January the difference was only 

 o°'8, and in this month the highest hourly mean occurred 

 during the night, and the lowest during the day. On the 

 other hand, the difference of the mean daily maxima and 

 minima for January was 6°7. In truth, the influence of 

 the sun on the temperature of the air is all but eliminated 

 during the winter months owing to the thick covering of 

 mist, fog, and cloud, in which the mountain is almost 

 constantly wrapped. 



Since June 18S1 the highest temperature on Ben Nevis 

 was 59 0, 3 on August 8, 1882, and the lowest 9°"9, on Feb- 



