86 



Sir RoLcrt Christison on the 



lieat. A natural result was that April failed to bring the 

 buds as usual to the point of expansion in May ; that a no 

 less ungenial May, barely brought them to that point in the 

 beginning of June ; and that every vegetable function must 

 have been more or less checked during the three subsequent 

 months. 



Thirdly, it is well-known that sun-light, apart from its 

 heating power, has an important influence on the activity, 

 and even the integrity, of various vegetable functions. I 

 am not aware of any inquiry having been made into the 

 question of its influence on the growth of tree-wood. But 

 there is no reason for supposing this function exempt from 

 such influence and at any rate it must be affected by the 

 mere heating power of the sun's rays. Now, every one must 

 have been struck with the extraordinary deficiency of sun- 

 shine during the growing months of 1879, and especially in 

 the months of May and June. Meteorologists have not yet 

 struck out a satisfactor}-- method of registering the amount 

 of daily sunshine. But the following observations are 

 worthy of notice as supplying comparative results. 



The Times newspaper gives the following observations 

 made at Greenwich Observatory with an instrument which, 

 during the daily progress of the sun, marks "bright sun- 

 shine " by discolouring or burning a card-board. Thus are 

 obtained the monthly hours of sunshine for 1878 and 1879, 

 as follows ; — 



The sun of Greenwich of course does not regulate the 

 sunshine of the Lothians and Strath-Tay. But the indica- 

 tions of its register are conformable with what was matter 

 of general observation all over Britain ; and such meteoro- 

 logical data as are attainable in regard to this locality, show 

 an inferiority of sunshine for Edinburgh in 1879, even 

 considerably greater than in the neighbourhood of London. 



