THE ROLLING CARRIAGE. '.»7 



Third sheet started at 4.34 p. in. at nearly 14 revolutions per minute. Four records obtained. 



Ended at 1.11 p. m. 



/,', ading of traces. 



Fourth sheet. Velocity about 20 revolutions per minute. Two records obtaine 

 at 4.57 p. ni. 



d. Ended 



Fifth sheet. Velocity about 25 revolutions per minute. Two records obtained. The first 

 record is good. The second record cannot be interpreted. Ended at at 5.15 p. m. 



The experiments were made from October 24 to November 2, L888, with a 

 short series on November 28, 1890, and embrace observations with 6, 8, and 12 

 inch square planes, those with the 6-inch plane extending over velocities from 7 

 to 30 meters per second. They are presented in extenso at the end of the present 

 chapter The extension of the spring is given in inches, as originally measured 

 from the trace, and the corresponding pressures are given in pounds and 

 grammes. The next succeeding column gives the pressure P in grammes per 

 square centimeter of the wind-plane surface. The last column gives the value of 

 the coefficient k m in the equation P= Tc m T' J , where 1' is the pressure in grammes 

 on a square centimeter of surface, and V the velocity expressed in meters per 

 second. The subscript m is used here, as in previous chapters, to designate these 

 metric units. 



One of the objects of the experiments was to test the generally accepted law, 

 that the pressure varies as the square of the velocity, and for this purpose 



13 



