193 



spoke in my first paper of the necessity for rain measurements 

 being continued for a long term of years " in order to determine 

 the true average fall at any particular place," and this necessity 

 is clearly shown in the present instance. The average Rainfall 

 in the Institution Gardens, as determined by ten years measure- 

 ment, is set in my former paper at 29-986, or allowing for errors 

 at 30 inches. Now — at the end of '^0 years, it is found to be 

 32-064inc., or more than two inches in excess of the ten years 

 measurement. 



But this is not the only striking circumstance in the com- 

 parison of the two decades. It may further be observed that 

 the excess of rainfall is almost entirely confined to the latter 

 decade, so that in a general way the first decade may be called 

 a dry one, and the latter a wet one. In the first decade there 

 are only three very wet years, or in which the rainfall amounted 

 to more than 30 inches. In the second there were seven such 

 years, the fall in 1882 being more than 42 inches. This last 

 year was the wettest of the whole twenty ; and not only that, 

 but in no other year did the rainfall attain even to 40 inches. 



Other wet years were 1866, 1872, and the five consecutive 

 years 1875 — 1879, in all which years the rainfall was between 

 34'953 inches and 37'795 inches. 



Thus, in consequence of most of the wet years occurring in the 

 second decade, the two decades are very unequal in respect of 

 rainfall ; the mean yearly fall in the first decade (1866 — 75) 

 being 30-504 inches, that of the second (1876—85) being 33-573 ; 

 the diflference between the two being 3*069 inches. 



The driest year in the whole series was 1870, when the rainfall 

 did not exceed 21 inches. The only other very dry year was 

 1873, when the rainfall as measured, was 2i-890 inches. 



Passing on to the consideration of the seasons. The following 

 table represents the mean, maximum and minimum rainfall 

 in each of the four seasons as the result of twenty years' 

 meaurement : — 



