396 



Dr Christison on the 



[sESS. 



Taking a general view of the annual aggregate variations 

 in the species, it will be seen from the Table that in the 

 deciduous class of 16 species the maxhnum, 11-36, occurred 

 in 1878, the first year of the decenniuni; that a progressive 

 decline took place to the minimum, 611, in 1880 ; that a 

 marked rally to 8-87 took place in 1881 ; that the rate con- 

 tinued much the same till 1884 ; and that it was reduced by 

 about an inch in the last three years, that for 1887 being 

 7-37. In the 9 evergreen species the sequence was different. 

 The maximum 8*27, indeed, was also in 1878, but there was 

 no rally in the third of the three succeeding hard years, the 

 amount falling on the third of them to about 6 inches, and 

 a rally to 7 in the next year was immediately followed by 

 a fall to 5 inches, the minimum, in 1883. In the next three 

 years there was a return to an average of about 6^ to 7 

 inches, Ijut in the last year there was again a fall to 5'80. 



