WIND PRESSURE. 575 



AUSTRALIAN OBSERVATORIES. 



Sydney — 153 miles per hour by Robinson's anemometer, cor- 

 responding to llTlbs. per square foot by Smeaton's and 22lbs. per 

 square foot by Crosby's rule. 



William slown, near Melbourne — 35lbs. per square foot by 

 Osier' t; anemometer. Wind from north. 



Flagstaff Gardens, Melbourne — SOlbs. per square foot by Osier's 

 anemometer. Wind, south-west. 



Domain, Melbourne — 70 miles per hour by Robinson's anemo- 

 meter, giving 24-51bs. per square foot by Smeaton's and lOlbs. by 

 Crosby's rule. More recently 60 miles per hour has been re- 

 corded by Hagemann's anemometer, giving ISlbs. or 9lbs. respec- 

 tively according to the above rules. During this gale a chimney was 

 blown over at North Melbourne, which. Avithout counting the 

 adhesion of the mortar, would require 20lbs. per square foot to 

 overturn it in one mass. 



Adelaide — 25lbs. per square foot by Osier's anemometer, 70 

 miles per hour by Robinson's, corresponding to 24-5lbs. per square 

 foot by Smeaton's or lOlbs. by Crosby's rule. 



The preceding results show extraordinary differences, and are 

 most perplexing to anyone engaged in the design of works, and 

 were the higher ones adopted as data for designing would involve 

 enormous increase in the expenditure upon many engineering and 

 architectural structures — in fact, would absolutely forbid the 

 existence of some of the most useful appliances of civilisation. 

 Leading British and American engineers, however, have, by- 

 common consent, disregarded them and based their practice upon 

 actual experience with engineering and architectural works. As 

 an example of this kind of experience the case of railway 

 carriages may be quoted. These are of approximately constant 

 dimensions. They exist in enormous numbers in almost every 

 part of the world. They are continually standing or running in 

 the most exposed positions on high embankments, or viaducts, and 

 their failure to resist wind pressure would lead to appalling 

 accidents that could not fail to be reported far and wide. And 

 what is the result? Why. simply this, that standard and Irish 

 gauge vehicles which calculation shows would overturn in various 

 cases with from 25lbs. to 3olbs. per square foot never do overturn, 

 unless exposed to a tropical cyclone of such intensity that towns, 

 houses, and ships are destroyed, and provinces depopulated by 

 them, and that narrow-gai;ge vehicles, which would overturn with 

 from 20lbs. to 30lbs. only, have been overturned so rarely, and 

 under such very exceptional circumstances only, that the public 

 make no objection to them on that ground. 



Further, though not quite so definite, evidence is obtained from 

 ■chimneys ; these exist in countless numbers and in the quaint 

 medieval styles of architecture now so popular are made com- 

 paratively tall and thin. There are thousands of such chimneys in 



