Nipher — Frictional Effect of Railway Trains upon the Air. 227 



been included in these reductions. In some cases the wind 

 was so strong as to greatly disturb the measurements. It 

 was found to be impossible to eliminate this effect. The 

 wind velocity could not be determined at stations where the 

 train came to rest, under the conditions which hold along the 

 track between cities. Only such work is included in the pres- 

 ent paper, as might be expected to lead to a fair approxima- 

 tion to the constant in Newton's equation. 



The investigation of this subject was made possible by the 

 co-operation of Mr. W. W. Baldwin, president of the St. L., 

 K. and N. W. R. R. and of Mr. A. W. Sullivan, General 

 Superintendent of the Illinois Central Railroad. Assistance 

 in making the measurements was also given by my colleague, 

 Professor Engler. 



Issued November 12, 1900. 



