The rate of the decrease of temperature with height there is 1 deg. Fahr. for every 275 feet of ascent, on the mean of the year. The rate is most rapid in April and May, when it is 1 deg. for each 247 feet; and least rapid in November and December, when it is 1 deg. for 307 feet. This rate agrees closely with the results of the most carefully conducted balloon ascents. The departures from the normal differences of temperature, but more especially the inversions of temperature, and the extraordinarily rapid rates of diminution with height, are intimately connected with the cyclones and anti-cyclones of North-Western Europe; and form data, as valuable as they are unique, in forecasting storms. The most striking feature of the climate of Ben Nevis is the repeated occurrence of excessive droughts. For instance, in the summer and early autumn of 1885, low humidities and dew-points frequently occurred. Corresponding notes were observed at sea-level. During nights when temperature falls through the effects of terrestrial radiation, those parts of the country suffer most from frosts over which very dry states of the air pass or rest; whereas, those districts, over which a more humid atmosphere hangs, will escape. On the night of August 31 of that year, the potato crop on Speyside was totally destroyed by the frost; whereas at Dalnaspidal, in the district immediately adjoining, potatoes were scarcely--if at all--blackened. The mean annual pressure at Ben Nevis was 25.3 inches, and at Fort William 29.8, the difference being 4-1/2 inches for the 4400 feet. For the whole year, the difference between the mean coldest hour, 5 A.M., and the warmest hour, 2 P.M., is 2 deg. For the five months, from October to February, the mean daily range of temperature varied only from O.6 to 1.5. This is the time of the year when storms are most frequent; and this small range in the diurnal march of the temperature is an important feature in the climatology of Ben Nevis; for it presents, in nearly their simple form, the great changes of temperature accompanying storms and other weather changes, which it is so essential to know in forecasting weather. The daily maximum velocity of the wind occurs during the night, the daily differences being greatest in summer and least in winter. A blazing sun in the summer daily pours its rays on the atmosphere, and a thick envelope of cloud has apparently but little influence on the effect of the sun's rays. Thunder-storms are essentially autumn and winter phenomena, being rare in summer.