4:34 



BEN NEVIS OBSERVATORY. 



At Ben Nevis Observatory during mist or fog the Wet Bulb not infrequently stands 

 a fraction of a degree higher than the Dry Bulb, as may be seen in the tables giving 

 the hourly readings in full iu the earlier part of this volume. In computing the mean 

 differences of Dry and Wet, these entries are included without any modification. 



Table IV. — The average monthly total Rainfall at each hour, with at the right the 

 average total for the whole month. These are given, 1st for Ben Nevis from 1st January 

 1885 to 31st December 1896, 2nd for Ben Nevis from 1st August 1890 to 31st December 

 1896, omitting the months of March and April 1891 and January 1892, and 3rd at 

 FortAVilliam for the same period. The self-recording rain gauge at FortAVilliam 

 Observatory was not in use during the three months mentioned above, and therefore the 

 same months are omitted from the short period of Ben Nevis' average, so as to make it 

 strictly comparable with FortAVilliam. 



Following these are the hourly departures of each section of the table adjusted for 

 difference of Midnight values. At the rio-ht hand of each of these tables is o-iven what 

 would be the mean hourly fall if the Rainfall were distributed uniformly over the day, 

 and the departures are the differences at each hour from this mean. 



Table V. — The average monthly total Sunshine at each hour of the day, with at the 

 right the average totals for each month, the possible Sunshine in each month, and the 

 percentage of this possible actually recorded. The "possible" for Fort- William Obser- 

 vatory is the computed time that the sun is above the visible horizon there, as explained 

 on page 7. The table contains, 1st the average amounts at Ben Nevis from 1st February 

 1884 to 31st December 1896, 2nd at Ben Nevis from 1st August 1890 to 31st 

 December 1896, and 3rd at FortAVilliam for the same period. 



It appears from the table that in each of the three months November, December, 

 and January, the average amount of Sunshine on Ben Nevis is greater than at Fort- 

 William. This is entirely due to the amount cut off by the hills in the morning and 

 evening, for at the mid-day hours the Fort- William totals exceed those of Ben Nevis. 



A comparison of the Sunshine recorded at Fort- William with what would be the 

 possible for that place, if it had a level horizon, gives the following percentage in each 

 month for the monthly totals in Table V. : — 



Months. 

 Percentage. 



Jan. 

 11 



Feb. 



20 



Mar. 



30 



Apr. 

 34 



May 

 35 



June 

 34 



July 

 23 



Aug. 

 20 



Sept. 

 2G 



Oct. 

 24 



Nov. 

 11 



Dec. 



7 



Year 

 25 



Table VI. — The mean hourly Wind-Force for each month at Ben Nevis Observatory 

 for the period 1st -January 1884 to 31st December 1896, followed by the departures of 



