172 REMARKS ON THE PRECEDING PAPER, 



an easterly set in this way between the S.W. and N.B. points of a 

 line joining Adelaide and Brisbane. But, whether this is due to 

 the general atmospheric translation from west to east, or to the 

 influence of a compound motion or resolution of forces of a 

 southerly wind and a westerly wind during gales, does not 

 appear. 



That gales which come in at Adelaide from the S.W. and blow 

 towards the N.E. in aright line, must by necessity have a seeming 

 tendency to the east, is clear ; but, it may be open to conjecture 

 whether gales which blow fiercely from the south would progress 

 to the eastward, unless the general westerly current could over- 

 power them. 



All this is on the supposition that such gales are right-lined, 

 It is doubtful, however, whether they are not actually circular, 

 and if it be so (and there can be no comparison as to the changes 

 of wind following the same order at Sydney as well as at Adelaide 

 and Brisbane, unless they are) the easterly progression must be 

 due to some other cause. 



I will state what I believe the cause to be. 



In dealing with storms in Australia we must well weigh all 

 the local conditions. Surrounded by wide oceans its coasts are 

 exposed to the prevailing ocean winds. Along the east coast, at 

 a moderate distance from it, runs a barrier of high land from 

 3,000 to 7,200 feet in elevation, separating the eastern coast from 

 the low interior, the southern part of which is exposed to the 

 S.W., say about Adelaide. 



The tendency of the drainage of the northern part of the 

 mountain barrier is (as shown by the Darling) in the same N.E. 

 and S.W. line of which, in reversed direction, storms are assumed 

 to travel from Adelaide to Brisbane. 



Now, it is reasonable to assume, that unless a storm has a 

 vertical thickness greater than the height of the Cordillera it 

 cannot cross it ; and, therefore, only such storms as are more 

 than from 3,000 to 7,200 feet thick can cross the mountains, even 

 if their area be wide enough : and thus many storms bringing 

 heavy rains from S.W. never cross to the eastward at all, but 

 travel along the western slopes of the Cordillera, leaving all the 

 eastward dry and only slightly affected by other atmospherical 



