PREFACE 



Shortly after the death of Professor Rowland in April, 1901, a com- 

 mittee of the Faculty of The 'Johns Hopkins University was appointed 

 by President Gilman to suggest to the Trustees of the University a plan 

 for a memorial of their colleague. The committee, consisting of Pro- 

 fessors Remsen, Welch and Ames decided to recommend that a volume 

 be prepared containing the physical papers and addresses of Professor 

 Rowland, and also a detailed description of the dividing engines which 

 had been designed and constructed by him for the purpose of ruling 

 diffraction gratings, and that this volume be published by the University 

 Press. This recommendation was approved by the Trustees of the 

 University; and the same committee, with the addition of Professor 

 R. W. Wood, was empowered to prepare the volume for publication. 

 The editorial supervision has been mainly undertaken by Professor 

 Joseph S. Ames. 



In deciding upon the scope of the proposed volume, it was thought 

 best to include only the distinctly physical papers, inasmuch as Pro- 

 fessor Rowland himself on several occasions when the question of the 

 collection of his scientific papers was raised, had expressed himself as 

 opposed to the republication of the purely mathematical ones. It was 

 also decided to omit tables of wave-lengths, as these are extremely 

 bulky, and copies can be easily obtained. Professor Rowland left many 

 thousand pages of manuscript notes and outlines of lectures, but none 

 of this material was ready for publication, and the committee were not 

 in a position to undertake the task of its preparation. No attempt has 

 been made to include a biography of Professor Rowland, for this would 

 properly form a volume by itself, and would require much time for its 

 preparation. There was at hand, moreover, the memorial address of 

 Dr. Mendenhall, which tells so well, though briefly, the story of his life. 



