98 TKANSACTIOXS AND PKOCEEUIXGS OF THE [Sess. lxii. 



the coincidence of sunshine and increment, it will require 

 to be explained in terms of temperature and moisture. 

 The six maxima agree still more closely with the periods of 

 maximum temperature, as each coincides with the tem- 

 perature at or above the mean. The three minima also 

 occurred when the temperature was considerably below the 

 mean. 



The 18 64 minimum followed the very cold summer of 

 1863, and in 1864 the temperature was only very slightly 

 above the mean. 



Let us now follow the curve in detail from 1856 onwards. 

 The rise from 1856 to 1859 took place during continuous 

 warm, dry, sunny, growing seasons. 



The fall of 1860 came witli a very cold, sunless, and 

 moist summer. The season of 1861 was warmer, but the 

 other conditions did not improve, and rainfall and humidity 

 were much above the mean. The cold of 1860 would allow 

 of very little reserve food, while the increased moisture of 

 1861 would hinder growth, and these two conditions are 

 sufficient to account for the continued fall in 1861. 



It is difficult to understand the rise of 1862, but the 

 increment forthat year is small when compared with the 

 five years preceding 1861, and it may partly be accounted 

 for by the lessened rainfall of 1862, although the tempera- 

 ture was below the mean. 



The very cold season of 1863, added to the relatively 

 cold season of 1862, brought about a further fall, which 

 was continued until 1864, wlien tlie first minimum was 

 reached. 



The temperature of April, May, and June 1864 fell 

 below the freezing-point, and this may have helped to 

 check the growth. 



From 1864 to 18 70 there was a steady rise, due largely 

 to the increased sunshine, higher temperature, and lessened 

 rainfall of those years, excepting the cloudy, colder, and 

 moister year of 1867, which caused a slight dip in the 

 curve. 



The temperatures of 1867 and 1868 were not suffi- 

 ciently far Ijelow the mean to do more than lower the 

 curve sliglitly in its upward rise, but in 1869 and 1870, 

 with warmer, sunnier, and drier seasons, the rise was rapid. 



