NA TURK 



261 



THURSDAY, JANUARY 22, 1SS5 



HIGH-LE I 'EL METEOROLOG V 

 Berii lit tiber die Errichtung der Meteorologischen Station 



auf don Sdntis und Hire Thaligkeit, September 1 SS3 



to August 1884. Erstattet von R. Billwiller. (Zurich, 



1884.) 

 Journzl of the Scottish Meteorological Society. Third 



Series, No. 1. 



WE briefly noticed at the time (NATURE, vol. xxix. 

 p. 413) M. Billwiller's first report on the Swiss 

 high-level station on Santis, in the Canton of Appenzell ; 

 and his second report has now come to hand, giving, 

 along with a rapid history of the establishment of this 

 first-class meteorological observatory and its equipment, 

 an excellent resume of two full years' observations, ending 

 August 31, 18S4. A comparison of the results with those 

 obtained for Ben Nevis presents several points of con- 

 siderable importance. 



On Siintis, 8094 feet high, the mean annual atmospheric 

 pressure is 22*237 inches, the highest monthly mean 

 being 22^429 inches in August, and the lowest 2i"993 

 inches in March. On Ben Nevis, 4406 feet high, the mean 

 annual pressure is 2i'25; inches, the highest mean being 

 2j"400 inches in July, and the lowest 25141 inches in 

 try. The differences between the highest and lowest 

 is thus o - 436 and 0^259 inch respectively. On Siintis the 

 mean annual temperature is 2S C '2, the highest monthly 

 mean being 41 = '4 in August, and the lowest i8 c, o in January. 

 The annual mean for Ben Nevis is 30°"9, the highest 

 monthly mean being 4l°'3 in July, and the lowest 22°'o in 

 February. The lower mean temperature of Siintis is 

 thus wholly due to its colder winters. 



But the most marked difference in the climates of the 

 two situations is revealed by the hygrometer. On Santis 

 the mean annual relative humidity for the two years is 

 S4, the highest monthly mean being 93 in September 

 18S2, and the lowest 71 in March 1SS4. On Ben Nevis, 

 on the contrary, the lowest mean monthly humidity was 

 90 for May [884, and the highest for January of the same 

 year, when the mean dry bulb was 25°'5o, and wet bulb 

 25 47, showing an approximate humidity of 99. Indeed, 

 so thick and continuous was the covering of mist, fog, 

 and cloud in which lien Nevis was wrapped during this 

 month, that the difference between the mean coldest and 

 warmest hour of the day in winter is only half a degree. 

 We have drawn attention (vol. xxx. p. 336) to the sudden 

 changes of humidity which characterise the climate of 

 Ben Nevis in connection with anticyclonic movements, 

 when the atmosphere passes rapidly from a state of the 

 most complete saturation to a state of dryness greater 

 than is ever reached at lower levels in this part of Europe, 

 and that on such occasions the temperature rapidly rises, 

 till sometimes it even rises higher than at Fort William, 

 about 4400 feet lower down. Now M. Billwillcr gives an 

 extremely valuable column in one of the tables, sho 

 the minimum relative humidity observed each month, 

 from which we see that a humidity of 21 occurn 

 August 1883, and that on six of the other twenty-three 

 Vol. xxxi— No. 795 



months a humidity less than 30 was recorded. The 

 importance of these observations from Ben Nevis ar.d 

 Santis on the great movements of the atmosphere in 

 cyclones and anticyclones, and on the Fohn and the 

 various theories that have been suggested in explanation 

 of its phenomena, need not here be insisted on. 



On Santis the annual rainfall, inclusive of melted snow, 

 was 67^83 inches. The heaviest rainfall of any month 

 was I5'I2 inches in July 1S83, and the lightest 071 inch 

 in February of the same year. On the top of Ben Nevis. 

 for the five months from June to October of 18S2 and 

 1883, the mean rainfall was 44'35 inches ; and on Santis. 

 for the same five months of 1S83 and 1S84, the rainfall 

 was 4395 inches — the summer rainfall of the two places 

 being thus nearly the same. These amounts are very 

 greatly in excess of what several theories of the distribu- 

 tion of the rainfall on the slopes and tops of mountains 

 would lead us to expect. In discussions of this question 

 it will be necessary to give more pointed attention than 

 has yet been given to the great vertical movements in 

 the atmosphere which are disclosed by the hygrometric 

 observations of these high-level stations. 



Of even greater interest are the hourly observations at 

 the two observatories, especially those relating to atmo- 

 spheric pressure and wind. At the two places the hourly 

 curves of pressure for different seasons run closely parallel 

 to each other. In June, when the more special features 

 of the curves are most pronounced, they closely approxi- 

 mate to a single diurnal minimum and maximum. The 

 minimum occurs from 5 to 6 a.m., and the maximum from 

 9 to 10 p.m., the daily range being 0x139 mcn on Santis. 

 and o'OjO inch -on Ben Nevis. Each curve shows an 

 extremely shallow secondary minimum from 5 to 6 p.m. 

 which, as compared with the secondary maximum imme- 

 diately preceding indicates a fall not exceeding C003 

 "inch. 



This secondary maximum occurs at 3 p.m. on Santis, 

 and at 3.30 p.m. on Ben Nevis, and is the analogue of the 

 morning maximum which occurs at lower levels in the 

 same localities six hours earlier. On Mount Washington, 

 United States, this maximum occurred in June 1873 at 

 8.30 a.m. at the base of the mountain, 2S98 feet above 

 sea-level, 10 a.m. at 4059 feet, 11 a.m. at 5533 feet, and 

 at noon on the top of the mountain at a height of 6285 

 feet. On Ben Nevis, while pressure is steadily falling at 

 the base of the mountain from 9 a.m. to 4 p.m., on 

 the peak it continues steadily to rise ; and the same 

 phenomena doubtless obtain at Santis. 



At the same time the diurnal velocity of the wind on 

 these peaks shows even a stronger contrast when com- 

 pared with the diurnal velocity at lower levels. At low 

 levels and on plateaux of considerable extent the velocity 

 of the wind falls to the daily minimum early in the morn- 

 ing, and rises to the maximum at or immediately after 

 noon, or about the time of strongest insolation. The 

 following table, showing the diurnal variation in the wind's 

 velocity on Ben Nevis, Santis, and Mount Washington in 

 summer, and on Ben Nevis in winter, presents for these 

 elevated peaks curves precisely the reverse of the curves 

 for velocity at lower levels. The figures express in per- 

 or defect of each hour's velocity from 

 the daily mean : — 



