BEN NEVIS OBSERVATORY. 435 



each hour from the monthly average, adjusted for the Midnight difference of value. A 

 description of the mode of observing the wind and the scale of force used will be found 

 on page 5. No wind observations are given for the Fort- William Observatory, as the 

 surrounding hills give the winds at that place a local character which renders them 

 useless for comparison with the winds observed at the summit of Ben Nevis. 



Table VII. — The mean hourly Amount of Cloud for each month at Ben Nevis 

 Observatory for the period 1st January 1884 to 31st December 1896 in the scale to 

 10, fog or mist when sufficient to hide the sky being reckoned as 10. Also the 

 departures of each hour from the mean monthly values adjusted for the Midnight 

 difference of values. At the Fort- William Observatory the Amount of Cloud is only 

 observed five times a day, and therefore no hourly values can be given. 



Table VIII. — The mean monthly temperatures in the Stevenson Screen at the Fort- 

 William Observatory (see page 6) at the hours of 9, 10, 14, 21 and 22, with the mean 

 Maximum and Minimum in the same Screen, and the means of the Black Bulb in vacuo 

 and Ground Radiation Minimum, for the period 1st August 1890 to 31st December 

 1896. Following this is the difference between the temperature in the Stevenson Screen 

 and that in the Thermograph Screen in which are the thermometers from which the 

 hourly values for the whole twenty-four hours are got, at the five hours for which 

 mean values are available in the Stevenson Screen, and for the Maximum and Minimum 

 temperatures. When the Stevenson is the higher, the difference is in heavy type, and 

 when lower in italic type. 



Table IX. — The frequency of the different winds at Ben Nevis Observatory, 

 expressed in percentages, for the period from 1st January 1884 to 31st December 1896. 

 The direction of the wind is noted at each hour, so that during the thirteen Januaries in- 

 cluded in this period there were 9672 observations of wind, and of this number 19*1 

 per cent, were N., 10'4 per cent. N.E., and so on, as given in the table. The values for 

 the year are the mean of the twelve monthly values for each direction. 



