METEOROLOGICAL OBSERVATIONS ON BEN NEVIS. 79 
January was a somewhat mild month, with the highest mean tem- 
perature since 1898, and both February and March were, at both 
Observatories, colder than January. On the whole, however, the deviations 
of temperature from the normal were in no way remarkable. The 
absolutely highest temperature during the period at Fort William was 
75°-5 on July 11 and 12, and on Ben Nevis 62°-1 on the former day, the 
lowest at Fort William being 24°°5 on March 15, and on Ben Nevis 
10°-1 on March 1. 
In Table III. are given for each month the lowest observed hygro- 
metric readings at the top of Ben Nevis (reduced by means of Glaisher’s 
tables) :— 
TasLeE IIT. 
1904 Jan. | Feb. | Mar. | April] May | June | July | Aug.| Sept. | Oct. | Nov. | Dee. 
° ° ° | ° ° ° ° | °o ° ° ° ° 
Dry Bulb . . | 20% | 22°2 | 268 | 30:3 | 31°0 | 49°5 | 55°8 5L1 | 44°6 — — —_ 
Wet Bulb. . | 17-4 | 180 | 20:7 | 25:3 | 24:0) 38:0 | 40°3 |} 442] 311) — — — 
Dew-point . . | -43 | -9°3 | -8°0 | 10:3 Bl | 25:7 | 263) 370 | 149) — — = 
Elastic Force. . | ‘035 | °027 | -029 | :069 | *054 | °139 | 143 | *220 | *085 | — — — 
Relative Humidity 32 23 20 41 31 39 32 59 29) — — = 
[Sat.=100] 
Day of Month : 31 17 24; 19 20 7 10 30 23) — — = 
Hour of Day . 24 14 23 | 4 7 9 14 2 22; — — — 
Of these relative humidities the lowest, 20 per cent., occurred on 
March 24 at 11 p.m. ‘he air on the summit had been very dry for 
several hours, but at midnight on the same day, or only one hour after 
the minimum humidity for the period had been recorded, complete 
saturation set in, an excellent example of the rapid changes of humidity 
so frequently observed on Ben Nevis. This sudden variation was not 
due to any change of wind direction, but to fog rising from the valleys 
and enveloping the mountain top. The longest spells of complete satura- 
tion were from January 8 to 22,and from 9 a.m. on March 31 to 8 p.m. on 
April 14. 
The rainfall for the nine months at the top was 121-44 inches, or 
10°51 inches above the mean of nineteen years ; whilst the aggregate at 
Fort William was 61-84 inches, or 9:02 inches above the average. for the 
same period. At both stations the amounts for April were much the 
largest recorded during twenty years, the rainfall at the top being more 
than thrice the normal. In that month there were on Ben Nevis twenty- 
eight rainy days, of which three had falls exceeding 2 inches, and no fewer 
than fourteen falls of more than an inch, the aggregate for the first ten 
days of the month being as much as 17:10 inches. At the summit station 
the greatest fall recorded in a single day was 2°69 inches on January 14, 
the corresponding fa]l at the base being 0-65 inch, whilst the maximum 
daily amount at Fort William was 2:07 inches on September 5, the fall on 
Ben Nevis on that day being 2:08 inches, or practically the same. 
At the top of Ben Nevis the number of rainy days during the period 
was 202, or ten above the average, and at Fort William 193, or seveuteen 
above the average. The number of rainy days in April and August was 
unusually large, and it may be noted that in January, May, and July there 
were more rainy days at the base of the mountain than on the top. The 
number of days with falls of 1 inch or over was, on Ben Nevis forty-four, 
or nine above the average, and at Fort William twelve, or two above the 
average. 
