IMPORTANCE OF FEDKAL HYDROGRAPHY. 



XXVII. 



vision may be sufficient to give an average idea of the 

 rainfall for a large district, but quite insufficient for an 

 exact statement of the rainfall over any particular river 

 basin or tributary ; again the altitude of the majority of 

 rain gauges not having been determined considerably dis- 

 counts their value, as for instance in the determination of 

 rainfall over a catchment area of fluctuating level, here 

 the existence of one gauge might afford an idea of the rain- 

 fall on other parts of the area at greater or less altitude 

 than that of the observing station, if by a series of obser- 

 vations elsewhere the ratio of increase or decrease of 

 rainfall had been determined for increase or decrease of 

 altitude. 



Investigating this question of altitude on rainfall the 

 author was much struck with the relation existing between 

 them on the line of the Great Western and Great Southern 

 Railways, and also along the line of the Dividing Range 



EFFECT 



ALTITUDE 





