18 EXPERIMENTS IX AERODYNAMICS. 



general of a succession of settings of the wind plane beginning with a setting at 

 !•(» and followed by diminishing angles of elevation. At each setting two obser- 

 vations are usually obtained by turning the register sheet through an angle of 

 L80 . Thus the two traces made at the same setting should lie in a straight 

 line passing through the center 



The method adopted in reading the traces is as follows: Straight lines, arc 

 drawn through the center and the two traces made at each setting of the plane. 

 The angle is then measured between the trace of the plane at 90° and the traces 



-responding to other settings. The pressure being normal to the plane, these 



measured values should be the complement of the angles of elevation at which 

 the plane is set. It will be seen by inspection of the accompanying tables thai 

 this relation approximately obtains. 



Tables II, III, and IV contain all the original data of the experiments and 



their reduction. The first columns require no explanation. The fifth column 



(Tables II and III) gives the angle measured on the register-sheet between the 



radial direction of each trace and the direction of the trace made when the plane 



was set vertical. The sixth column gives the measured distance of the trace from 



the center, and the seventh gives the results of these extensions converted into 



p 

 pressure on the plane by means of Table I. The column headed k m = ~ contains 



the results of measurements of pressure on the normal plane expressed in terms 

 of the coefficient k m of the equation P = k m V~, in which Fis the velocity of the 

 plane in meters per second and P the pressure on the plane in grammes per square 

 centimeter, the subscript m being used to designate units of the metric system. 



