DEPICTING DIAGEAMMATICALLY THE CHARACTER OF SEASONS. 67 



on the diagram a curve with increasing radius the direction of 

 which more nearly approaches the horizontal as time goes on. 



The curves have been arrived at by a tentative process in the 

 first instance, but I am convinced that the results on the whole 

 are fairly representative of the actual facts. With careful study 

 and experiment, probably a considerable degree of exactness could 

 be arrived at. 



The diagrams of the years 1883 to 1899 inclusive, are based on 

 rainfalls recorded by myself from time to time at my residence on 

 the Parramatta River. The records for 1883 and 1893 are 

 unfortunately incomplete. 



Diagrams of this kind might be plotted so as to represent, with 

 very great accuracy, the combined effect of the weather conditions. 

 The daily evaporation due to dry winds and high temperatures, 

 and reverse conditions could be taken into account, and once the 

 right equation is found, x being the inches of rain required for 

 complete saturation, the angle of descent could be calculated. On 

 the other hand I have little doubt that an empirical method for 

 •obtaining the proper curves to use for each set of weather con- 

 ditions would come pretty near the truth. What is wanted is to 

 represent the character of each drought so as to be able to compare 

 it with those of others of the same locality. 



Of course any diagram would in all its details only apply to 

 the district over which the same conditions extended. On other 

 soils and with other climatic conditions one would get somewhat 

 distinct results. 



It is not to be expected that one set of diagrams would suit a 

 whole country or even a whole district any more than one set of 

 thermometers and one rain gauge would serve, but for those who 

 like to try the method, I would say that the diagrams are rapidly 

 done, when once the curves are decided upon. 



The black line is what I have called the " drought line " or the 

 curve of drying. The space between that line and the top line or 

 line of saturation, shows the dryness or droughtiness of the period. 



