VI PREFACE. 



My hearty tLauks are clue to several friends at Cleveland wlio liave given very 

 substantial aid. Mr. C. F. Wason presented me with an electric motor which has 

 been of great service. Messrs. Warner and Swasey have repeatedly sent at Christ- 

 mas a receipted bill for the considerable amount of work whidi had been done foi- 

 me at their shops. Mrs. Amasa Stone has generously given the means foi- pur- 

 chasing many conveniences which have much facilitated the work. The East 

 Cleveland Railroad Company kindly connected my private laboratory with their 

 lines, and they, as well as the present corpoiation, The Cleveland Electric Railway 

 Company, have supplied electricity for the uses needed in this work. And the 

 Smithsonian Institution purchased and lent to me the admirable balance witii 

 which most of the work on the densitv of the gases has been done. To all tliese I 

 desire to express my cordial thanks in connection with this account of the woi'k to 

 which they have so helpfully contributed. 



Edward W. Morley. 



