DISCUSSION. 105 



pressure plate for measuring the strength of the wind rested upon 

 springs, so that when the wind blew upon the pressure plate 

 against the springs, by a simple contrivance a pencil marked on 

 the chronograph the strength of the wind and the exact time 

 when it occurred. But it always appeared to me that these 

 springs were not fitted with the mechanical appliances that should 

 be applied to them, because we very well know that if we strike 

 any substance resting upon springs, there is a kind of impulse 

 given to it which scarcely measures the exact force of the blow. 

 I do not know whether any other contrivance has been adopted 

 for this Anemometer or not, but I had an idea at the time (I did 

 not finish this Anemometer I was about to construct) that another 

 contrivance would measure it better, and that was by having a. 

 chain weight attached to it. I would ask Mr. Russell what 

 improvements have been introduced since the pressure plates 

 rested on springs. 



Mr. Russell : — A great many methods of supporting the plate 

 have been tried, but the one most in favour is hanging the 

 plate on four springs, thereby endeavouring to get rid of friction ; 

 but all the methods are subject to the defect I pointed out, that 

 these violent gusts come along and have the effect of striking the 

 pressure plate like a hammer. It is quite recognised that it does 

 not record the pressure of the wind exactly. Some of the effects 

 of the pressure of the wind are almost incredible. I have an 

 account of a tornado which passed through the bush near Cobar. 

 It cut a narrow lane through the bush, breaking off short every 

 tree in its path, some of them 18 inches in diameter ; shrubs were 

 torn up by the roots, and the tops of large trees forced along the 

 ground after they had fallen, so making grooves in the ground 

 like a plough, and the circular motion of the wind could be seen 

 in the arrangement of the fallen timber. If such a storm ever 

 passes over Sydney there will be many wrecked houses. We 

 know nothing of the velocity of the wind in these terrible 

 tornados. Anemometers made light to record ordinary storms 

 are broken directly by such violent winds, and we can only judge 

 of the velocity by the force shewn in breaking great trees, 

 destroying houses, &c. 



Hon. G. H. Cox : — Can Mr. Russell give even a guess as tO' 

 the enormous velocity of the wind to create such destruction as 

 that % I can remember many years ago where in a track for 20 

 miles through the bush the trees were twisted off. What would 

 be the velocity of the wind to cause such enormous destruction 

 as that % I mean a velocity not only to turn over an engine but 

 houses almost in the streets of the city. 



Mr. Russell : — I am afraid I could not give a guess. We 

 have records which shew that the wind must have exerted a 



