Exact Measurement of Trees. 



87 



The following Table is extracted from a register of sunshine 

 kept for tlie Meteorological Society by their Edinburgh 

 observer, Mr Blackwood, and kindly communicated to me 

 by Mr Buchan. The daily hours of bright sunshine are 

 put down by the observer from estimate. The results 

 therefore are only approximate ; but as the system of 

 estimate is always uniform, these results must be at all 

 events fairly comparative. 



Professor Piazzi Smyth, Astronomer Royal, has also had 

 the kindness to communicate to me a similar tabular view, 

 deduced from observations made on the relative degree of 

 cloudiness. The data are taken from daily general obser- 

 vation of the state of the hemisphere, complete obscuration 

 by cloud being assumed at 1000, These data, says Professor 

 Smyth, are derived from " a very rough and simple kind of 

 observation, never intended for any grand meteorological 

 purpose ; but having been continued with regularity and 

 honesty during a long period, they do seem now capable 

 of some special results." It is to be hoped that the details 

 of his results may find a fitter opportunity for publication 

 by so able an observer. The only conclusions suitable in 

 the present sketch are those which regard the relative 

 seasons of 1878 and 1879, The mean cloudiness of the 

 summer months of 1876-7-8-9 was 721 ; and that for 1879 

 was 854, or a ratio of nearly 100 to 120. In 1878 the mean 

 of June and July was 704, and in 1879 it was 855-5, being a 

 ratio of 100 to 121'5, 



