268 
tion. His restless ingenuity was ever ready 
for any demand, and his mechanical apti- 
tude was so directed by a delicate cesthetic 
sense that he could never be satisfied with 
any objective proof which was not neat and 
simple, as well as adequate. A few of these 
he published from time to time. Among 
them may be mentioned methods of meas- 
uring the angle of inclination of the mir- 
rors employed in Fresnel’s interference ex- 
periments; of obtaining a permanent trace 
of the oscillation plane of the Foucault 
pendulum; of registering and exhibiting the 
vibration of rods; of deducing the funda- 
mental laws of electric repulsion by means 
of the pendulum; of measuring potentials 
and specific inductive capacities with the 
spring balance electrometer; of proving 
Ohm’s law, and of expressing electric po- 
tential as work. Many of his demonstra- 
tions in acoustics were gathered into a small 
volume on ‘Sound,’ and have thence been 
copied into the elementary text-books of 
to-day. The same may be said of a little 
volume on ‘ Light,’ prepared with the co- 
operation of Mr. Charles Barnard. In the 
student laboratory he was as efficient as in 
the lecture room, fertile in devices and ever 
insistent upon a high standard of accuracy. 
No one knew better than he that demon- 
stration and practice work are of insignifi- 
cant value in comparison with investiga- 
tion; but he kept always in mind the fact 
that, in America at least, the physical in- 
vestigator is nearly always compelled to be 
in some way a teacher, and that in teaching 
physical science demonstration and theo- 
retic instruction must go hand in hand. 
He was conscious of his skill and, naturally, 
took keen pleasure in exercising it success- 
fully. hatin so doing he gave pleasure 
and help to others is manifested by the ex- 
tent to which his methods have served as 
models. 
The manipulative skill and tactile deli- 
cacy which are so necessary as adjuncts to 
SCIENCE. 
[N. §. Von. VI. No. 138. 
independence and ingenuity in the labora- 
tory were applied with no less suecess by 
Professor Mayer in out-door recreation. 
Early in life he became an accomplished 
marksman ; and during manhood, as long 
as good health lasted, he was an ardent 
and exceptionally successful sportsman. 
His field and laboratory interests were 
combined in his application of the tuning 
fork to the problems of gunnery. In the 
Century Magazine he published a number 
of articles on sporting subjects. These 
were incorporated, along with contributions 
from other sources, in a volume entitled 
‘Sport with Rod and Gun in American 
Woods and Waters.’ This volume was 
edited by Professor Mayer, and for it he 
specially prepared two valuable articles, 
one on ‘The Shot Gun,’ and another on 
‘The Blow Gun.’ 
In addition to these literary labors, Pro- 
fessor Mayer contributed many articles to 
the Cyclopedias of Appleton and Johnson, 
besides occasional popular articles on scien- 
tifie subjects for other media of publication. 
In acknowledgment of his earlier contribu- 
tions to science the degree of Doctor of 
Philosophy was accorded him in 1866 by 
Pennsylvania College. He was admitted 
to membership in the National Academy 
of Sciences in 1872, and was a member of 
each of the leading scientific societies of 
America, besides being a corresponding 
member of the British Association. He 
served during one year, 1873, as an asso- 
ciate editor of the American Journal of 
Science, and during the first eight months 
of that year five articles from his pen ap- 
peared in its pages. The partial failure of 
his eyesight then necessitated cessation 
from all work, and a considerable part of 
the next scholastic year was spent in Hng- 
land, where his reputation had preceded 
him and where hospitable entertainment 
was accorded by the most prominent repre- 
sentatives of science. 
