630 MR R. C. MOSSMAN ON 



features of the meteorology of the Glen. The discussion is treated in three 

 sections : — 



I. General climatology of the Glen as compared with the Ben Nevis and Fort- William 

 Observatories, including diurnal ranges of pressure, temperature, and humidity. 



II. Observations taken during true " Fohn," and in a special type of rainy weather 

 in which a Fohn effect prevails in the Glen. This includes a discussion of the diurnal 

 period at the three stations as well as of observations taken on the adjacent hills during 

 excursions. 



III. Comparison of the meteorology of the three stations during periods of high 

 barometric pressure and low temperature, including observations taken on excursions 

 during the prevalence of " up-bank thaw." 



As far as possible, overlapping and repetition have been avoided in dealing with 

 the various sections, though this has been a matter presenting considerable difficulty. 

 It is for this reason that a detailed comparison of the monthly and other differences 

 between Glen Nevis and Fort- William in the matters of temperature, pressure, rainfall, 

 etc., has not been made, as the salient features are discussed in the sections dealing 

 with Fohn and up-bank thaw. 



The Characteristics of the Period October 1901 to February 1902 at the Ben Nevis 

 and Fort- William Observatories, as compared with the Normals. 



Table I. gives the mean values of the principal climatic elements for the months 

 October 1901 to February 1902 at the Ben Nevis and Fort- William Observatories, and 

 also at Achariach ; and in Table II. the data from the two former stations are compared 

 with their respective normals for the thirteen years 1891-1903. As regards cloud and 

 wind direction on Ben Nevis, the means are those of the twenty years 1884-1903. 



Looking at Table II., it will be seen that the characteristic features of October 1901 

 were a slight excess of pressure, rather low temperature, deficient sunshine, and slightly 

 increased cloud amount and wind force on Ben Nevis, accompanied by a rainfall 

 32 per cent, above the normal. Associated with this there was a marked excess of 

 southerly and defect of northerly winds. At Fort- William, pressure, temperature, 

 and sunshine were in close accordance with the average, but rainfall was a fifth greater 

 than the normal. 



The outstanding features of November on Ben Nevis were a high barometric 

 pressure, low temperature and wind force, and a slight excess of sunshine. In spite 

 of the high pressure, precipitation was but little below the normal, and this relatively 

 large rainfall was accompanied by a great excess of northerly and deficiency in southerly 

 winds. At Fort- William the observed departures were in close accordance with those 

 noted on the summit, but rainfall was distinctly below the normal. 



In December, on the summit of Ben Nevis, there was a low barometric pressure, 

 temperature, and wind force, accompanied by a normal amount of sunshine. Kainfall 



