May 3, 1901.] 
thing to our knowledge he devised many 
experiments which were carried out by his 
students under his immediate direction ; 
of these the most important were the one 
performed by Professor Hall, which led to 
the discovery of the ‘Hall effect,’ and 
those recently performed by Dr. Gilbert, 
which have led to purely negative results. 
Becoming interested in the study of spec- 
trum analysis, largely through the influence 
of his colleague Professor Hastings, he real- 
ized the importance of securing as perfect 
gratings as possible. So he constructed a 
dividing engine for the ruling of gratings, 
the essential parts of which were a screw of 
nearly perfect uniformity of pitch and a 
most ingenious device for the correction of 
periodic errors. With this machine many 
gratings were ruled on both glass and 
speculum metal, the surfaces being plane. 
But the idea occurred to him to investigate 
the action of a grating ruled on a spherical 
concave surface ; he discussed the question 
mathematically and thus discovered the 
great advantages of such ‘ concave grat- 
ings,’ and proceeded at once to rule them. 
(It should be noted that all the gratings, 
both plane and concave, which have been 
ruled under Professor Rowland’s direction 
and are now in use in all the physical 
laboratories of the world, have been sold at 
such prices as simply paid the wages of the 
laboratory mechanician who supervised 
their construction.) With these gratings 
the study of the solar spectrum was begun ; 
and in order to supplement eye-observa- 
tions, he made a careful study of photo- 
graphic methods, and prepared his own 
‘photographic plates. Having mapped the 
whole solar spectrum from the extreme red 
to the limits in the ultra violet, he had 
enlarged maps prepared and offered to the 
world. Then he undertook the systematic 
study of the arc-spectra of all the elements, 
so far as possible; and the final results of 
this long research are now nearly ready for 
SCIENCE. 
683 
publication. Within recent years his at- 
tention had been called to the theory of 
alternating currents and to their applica- 
tion for practical purposes. He devised a 
system of multiplex telegraphy depending 
upon synchronous motors, which received 
a grand medal at the Paris Exposition of 
1900. i 
These are but the most important of Row- 
land’s contributions to science ; a complete 
list would be even more striking. Far more 
important, however, than the results of the 
investigations themselves, is the spirit, the 
aim of the man as made manifest in them. 
His great purpose was to discover not sim- 
ply the truth in nature, but the deeply hid- 
den truth. Questions pertaining to the 
fundamental properties of electricity, mag- 
netism, ether and matter were always in his 
mind ; the exact measurement of spectrum 
lines was interesting to him only in so far 
as the results might lead to accurate knowl- 
edge of molecular constitution or of solar 
and stellar phenomena; all instruments or 
methods perfected by him were those which 
could be used to measure the great constants 
of nature. 
To appreciate properly Rowland’s great- 
ness as an investigator one must have 
worked with him. He enjoyed to the ut- 
most the rare gifts of intuitive knowledge 
and of self-confidence. His energy, his 
manual dexterity, his ingenuity, his keen- 
ness in perceiving and avoiding experi- 
mental errors, his skill in devising appar- 
atus, were always evident. No scientist of 
this generation has had greater power than 
he of using his imagination under the re- 
straints and guidance of scientific knowl- 
edge. 
As the director of a great physical labor- 
atory, Rowland was in some ways unique. 
His enthusiasm and the inspiration of his 
example were always of the greatest help ; 
his suggestions were invaluable; but his 
critical powers, his deep insight into any 
