DEPICTING DIAGRAMMATICAL!/? THE CHARACTER OF SEASONS. 63 



SUGGESTIONS for DEPICTING DIAGRAMMATIOALLY 

 the CHARACTER of SEASONS as regards RAINFALL, 



AND ESPECIALLY THAT OF DROUGHTS. 



By H. Deane, m.a., m. Inst, c.e., &c 



[Read before the Royal Society of N. 8. Wales, July 5, 1899.'] 



The usual methods of plotting the rainfall which merely show in 

 some form or other the quantities of rain which have fallen dur- 

 ing a period, do not altogether achieve the desired result. 

 Generally speaking people are apt to judge of whether a particular 

 season is to be placed in the category of droughts or of good 

 seasons, according as the total rainfall has been below or above the 

 average respectively. It need scarcely be pointed out that any 

 conclusion thus arrived at must be entirely erroneous. It not 

 infrequently happens that a few months of droughty conditions 

 are followed by one or more months of excessive rainfall, by means 

 of which the total rainfall has been brought up to or above the 

 average. Judging by averages the whole period would pass as a 

 good one, whereas the dryness of the earlier part of the period 

 may have resulted in disaster, which is not at all compensated for 

 by the subsequent excessive rain, the greater part of which runs 

 to waste. 



The value of a year's rainfall is therefore not to be reckoned by 

 the total, but by the manner in which it falls and its distribution 

 throughout the year. Thus looked at, a year's rainfall under the 

 average coming at proper times may produce very much better 

 results than one that comes at unsuitable times, or that falls on 

 few occasions in excessive quantities with long dry gaps in between. 



My method will be seen to be particularly useful in reviewing 

 rainfall as affecting agriculture, but it also has the advantage of 

 showing what portion of the rainfall runs off the ground or soaks 

 away and is available for storage and for keeping up the flow of 

 rivers and streams. 



