74 Ogden Nicholas Rood. 



the principles involved in physical phenomena, and a keen 

 intuition of the experimental conditions and methods leading 

 to discovery. He was especially apt in the use of simple 

 means for the study of the problems which interested him, 

 often reaching results of great importance and novelty by the 

 skillful combination of pieces of the most ordinary materials, 

 such as are found in the physical laboratory. While appar- 

 ently caring little for the exhibition of mechanical expertness, 

 or for the attainment of mere elegance of design or finish, 

 he possessed constructive faculties of a high order, in the 

 adaptation of an apparatus for the purpose he had in view. 

 Many of his most striking researches were conducted with 

 scarcely any use of the standard instruments of the labo- 

 ratory, his experiments being carried out with means impro- 

 vised for the occasion, and gradually developed to greater 

 and greater elaboration, as new suggestions came to him 

 in the course of the work. In many cases this resulted 

 in notable improvements of familiar apparatus, and the pro- 

 duction of instruments of unexampled sensibility, and the 

 attainment of a degree of precision far beyond anything hith- 

 erto reached. Excellent examples of this are seen in his 

 improvement of the horizontal pendulum, by which he was 

 enabled to detect and measure changes of dimension in solid 

 bodies as small as the ten millionth part of an inch ; in his 

 modification of the Sprengel pump, by which he was able to 

 carry the exhaustion to degrees almost unlimited, and to meas- 

 ure tensions as low as the four hundred millionth of an atmos- 

 phere ; and finally, in the last research of his life, in which, by 

 the use of an electroscope of the most elementary simplicity, 

 he succeeded in measuring resistances of hundreds of thou- 

 sands of megohms, and detecting peculiarities of insulating 

 bodies hitherto unknown. 



After entering upon his scientific career Professor .Rood dis- 

 played great activity, and was a frequent contributor to this 

 journal, where most of his papers were published. The num- 

 ber of titles of his communications is about seventy, not 

 counting various minor contributions and notices. Though 

 many of them are quite brief, they would be sufficient, in 

 the aggregate, to form a volume of several hundred pages. 

 The number and variety of these papers forbids anything like 

 a full enumeration here, but some of the more characteristic 

 may be briefly mentioned. While at Troy University he 

 devised certain adaptations of the compound microscope for 

 measuring the angles of crystals, and indices of refraction ; 

 studied the stauroscope of Yon Kobell, and made new appli- 

 cations of it ; observed the singular contraction of the muscles 

 caused by contact with rapidly vibrating bodies, resulting in 



