278 H. C. RUSSELL. 



A MAP SHOWING THE AVERAGE MONTHLY 

 RAINFALL IN NEW SOUTH WALES. 



By H. C. Russell, b.a., c.m.g., f.r.s. 

 [With Plate XXXIX.] 



[Bead before the Royal Society of N. 8. Wales, November 7, 1894.'] 



It will be remembered that just twelve months since I brought 

 before the Society a Pictorial Rainfall Map giving the result of 

 many years of observation condensed into a few figures, and show- 

 ing the average rainfall on each square degree of New South 

 Wales. I have now the pleasure of bringing under your notice 

 another pictorial rain map, this time showing for each square 

 degree of this Colony the average quantity of rain which falls 

 in every month of the year. This is the first time such a map 

 has been prepared, and it conveniently answers questions of 

 great importance in agriculture, and so far as I am aware, 

 these questions are more fully answered by this map than by any 

 map or publication for any other country. 



At first sight the map looks like a confused mass of figures, but 

 that impression disappears as soon as the method of arranging the 

 figures is understood. In the first place each square degree in 

 the Colony is treated as quite independent of all the others, and 

 the average rainfall in that degree for each month of the year 

 was calculated from the rainfall records in it. The quantities of 

 rain in each month are then expressed in the usual way in inches 

 and hundredths of an inch,- and the months of the year are 

 arranged in four rows, each row covering a quarter of the year, 

 thus the first row in each degree reads January, February, March ; 

 the second April, May, June ; the third July, August, September;, 

 the fourth October, November, December. 



Now let us assume we want to know what rain to expect in each 

 month in some particular place ; say Bourke, we refer to the map 

 and find it is situated in a degree in which the average rainfall 

 for January is 2-63", for February 2-00", for March 2-06", for 



