THE 



AMERICAN JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



C. D.WALCOTT. 



Aet. XXYII. — The relation between Wind Velocity and Pres- 

 sure ; by H. Allen Hazen. 



For more than a century physicists have attempted a solution 

 of the problem with regard to the relation between wind- 

 velocity and pressure ; yet the experiments tried by different 

 observers and under varying conditions have often been con- 

 tradictory and difficult to reconcile. Two methods of investi- 

 gation have been very frequently adopted, the one by carrying 

 a plate either in a straight line or in a circle, and the other by 

 allowing a current of air to impinge normally upon the plate. 

 The pressure has been measured by using delicate appliances 

 on the plate ; but it will be readily seen that there must be great 

 uncertainty in such measurements, if made at the extremity of 

 a long arm, and, moreover, the use of any attachment what- 

 ever to the plate would tend to dampen the effect we wish to 

 measure, i. e. the plate would be restrained from following the 

 actual movements imposed upon it by the accumulation or flow- 

 ing off of the air from its front. 



Borda's experiments. — Perhaps the most reliable of the earlier 

 results are those by Borda in 1763. He used a kind of fly- 

 wheel, with vertical axis and a horizontal arm a little over 7 

 feet in length. On the end of this arm he placed the flat plate, 



Am. Jodr. Sci— Third Series, Vol. XXXIV, No. 202.— Oct., 1887. 

 16 



