While meteorological observations taken in deep narrow valleys are open to grave objection for many meteorological purposes, including the drawing of isobaric and isothermal charts, yet the study of the climatic features in such a locality presents several points of special interest. This is more notably the case in the present instance owing to the close proximity of the Ben Nevis Observatory and the low-level Observatory at Fort-William. As the latter was only about 4½ miles distant from the valley station, the peculiarities of the climatology of Glen Nevis could be studied with a confidence which would have been unattainable without this adjoining sea-level station.

In the year 1896 the Directors of the Ben Nevis Observatories arranged that a temporary observing station be opened at the hut on the road half-way up the hill. A barometer, rain-gauge, and set of thermometers were provided, also a Richard barograph, thermograph, and hygrograph. The hut stands on steeply sloping ground facing westward, and is 2190 feet above sea-level. The barometer and barograph were placed in the hut; and two Stevenson screens for the thermometers, the thermograph, and the hygrograph were placed on the hill-side in its vicinity along with the rain-gauge. Though the site was not an ideal one for the purpose, being on the side of a hill and not on a peak, it was considered that valuable information as to the condition of the air between the level of the sea and that of the summit might be obtained by occasional periods of observation at this Mid-Station. This expectation has been realised, especially as regards the distribution of temperature in summer.

Tables have been prepared of the average temperature at the Ben Nevis and Fort-William Observatories on each day of the year, using the records of the twenty years 1884 to 1903 inclusive. Table I. gives the average daily temperature at Ben Nevis, Table II. that at Fort-William, and Table III. the differences between them. These tables have been prepared as follows :—

Ben Nevis Observatory.—In summer the dry- and wet-bulb thermometers were exposed in an ordinary Stevenson screen 4 feet above ground, and in winter in a smaller-sized double-louvred screen, placed on a ladder-like stand, and moved up or down so as to be always about 4 feet above the surface of the snow. These thermometers were read hourly, and the average of the dry-bulb readings for the 24 hours of each day is taken as the temperature of that day. Table I. is the arithmetical mean of the values so computed on each day of the year.

The immediately preceding paper deals with the average difference of temperature between Ben Nevis and Fort-William throughout the year, but the difference often departs widely from these average values. The greatest departures from the average during the time that hourly readings are available at both places, viz. from 1st August 1890 to 30th September 1904, were Ben Nevis 17°·6 warmer than Fort-William at 9 A.M. on 19th February 1895, and Ben Nevis 28°·8 colder than Fort-William at 2 A.M. on 19th December 1890, being respectively 33°·3 below and 13°·1 above the mean difference, which is Ben Nevis 15°·7 colder than Fort-William.

The weather conditions on the summit of Ben Nevis made it impossible to obtain a continuous record from self-registering anemometers at the Ben Nevis Observatory, but we have in the hourly observations of the wind made by the observers what approximates to a complete and continuous record. The direction and strength of the wind were noted at each hour by day and night, and these observations are to be found tabulated month by month in extenso in this and the preceding volumes of observations. The direction is recorded to 16 points (N., N.N.E., N.E., E.N.E., E., etc.), and the pressure on a scale from 0 to 12 closely akin to the well-known Beaufort scale ; but the situation of the Observatory rendered the record of the wind-pressure or velocity very unsatisfactory.