388 GENERAL PROPERTIES OF CERTAIN PARTIAL DIFFERENTIAL EQUATIONS, ETC. 



I bad devised no simple means of determining the lower orders of motion in terms of the higher 

 orders but bad merely derived the higher orders from the lower by obvious processes of differentiation. 

 In Professor Rowland's paper an elegant solution of the much more difficult problem is given. I may 

 further say that up to the time of my becoming acquainted with Professor Rowland's research I had 

 found no physical interpretation of these quantities so that the entire credit for the development of the 

 theory of these motions is due solely to Professor Rowland. In the present paper the quantities corre- 

 sponding to the higher orders of motion are denoted by the letter v; with different accents and subscripts. 

 M>, work on the subject of the higher orders of motion is to be found in the paper quoted at the beginning 

 of this article, "General Properties of the Equations of Steady Motion. - ' I believe that Professor 

 Rowland has made no use of the integrating factors which I have there introduced. This part of the 

 subject I hope to go into quite fully in Part II. of the present paper. 



■Washington, D. C. 

 January 2, 1881. 



