Isherwood

which were the first to indicate that the classical
theories of Watt, Mariotte, and Gay-Lussac con-
cerning the expansion of steam had practical lim-
its, and that steam engines designed from these
theories alone were not necessarily the most ef-
ficient. Isherwood demonstrated that with in-
creasing ratios of expansion, cylinder condensa-
tion losses became larger while the additional
work gained from the increased expansion be-
came progressively smaller. He then concluded
that for every actual steam engine there is a lim-
iting ratio of expansion, beyond which econom-
ical expansion is impossible. He determined the
limit of efficient expansion for the engines of the
Michigan, and because it occurred at such an
early point in the stroke his results were imme-
diately attacked. His work was soon confirmed
by the independent work of Tyndal and Mayer,
however, and Engineering Researches, translated
into six foreign languages, became a standard
engineering text and remained for many years a
basis and a pattern for further experimental re-
search.

In 1861 Isherwood was appointed engineer-in-
chief of the navy and in 1862 became the first
chief of the bureau of steam engineering. When
the Civil War began, the steam navy consisted
of six frigates of low power, six sloops of war,
nine gunboats, two dispatch boats, and five side-
wheel vessels of small power. At the end of the
war there were 600 steam vessels of all descrip-
tions in commission. Isherwood personally di-
rected the design and construction of the machin-
ery necessary to accomplish this expansion. His
work was the target of much criticism, however,
of which The Navy of the United States (1864),
by E. N. Dickerson, and A Brief Sketch of Some
of the Blunders in the Engineering Practice of
the Bureau of Steam Engineering in the U. S.
Navy, by an Engineer (1868) are typical. The
chief criticism in the latter brochure was that
Isherwood made the machinery of his boats heav-
ier than was customary at that period; but, as
Isherwood explained, this was an extra precau-
tion against inexperienced handling by war per-
sonnel and an insurance against breakdown in
action (of which there were remarkably few in-
stances). Probably his most famous design was
the Wampanoag class of sloops-of-war, the ves-
sels from which the present type of light cruiser
developed. These sloops-of-war were designed
as "commerce destroyers" (a term and function
said to have originated with Isherwood) and
were developed to blockade the coast of the Con-
federate States* The Wampanoag class is spoken
of as the invention of Isherwood, who in addi-
tion to designing the machinery suggested the

Isom

principal dimensions of the hull. When built, the
vessels were the fastest in the world. The Wam-
panoag attained a speed of 17% knots an hour, a
speed which practically every naval expert had
declared to be impossible.

Isherwood remained as chief of the bureau of
steam engineering for eight years. "He was the
handsomest man in Washington in those days,"
according* to R. H. Thurston (in Gassier3s Mag-
azine, post, p. 345) ; "his curling black hair set
off to great advantage rarely excellent features,
and while men were interested in his always en-
tertaining . . . conversation—he was a great
conversationalist—the ladies and the photogra-
phers agreed in a more aesthetic view of the
man/' After being relieved as chief of the bu-
reau, he spent the remainder of his active service
largely in the study of foreign navies and naval
bases, and in the direction of experimental naval
researches as the presiding officer of special naval
boards. His work at the Mare Island Navy Yard
(1869-70) included a series of propeller experi-
ments, the results of which were notable contri-
butions to knowledge in this field (details of his
experiments are given in A. E. Seaton, The
Screw Propeller, London 1909). He was retired
June 6,1884, as a chief engineer, the highest per-
manent rank in the engineer corps, with the rela-
tive rank of commodore, and made his home in
New York where he wrote many articles for the
Journal of the American Society of Naval Engi-
neers. He was thirty-one years on the retired list.
At the time of his death in New York City, he
held the relative rank of rear admiral. The steam
engineering building at the Naval Academy, An-
napolis, was named Isherwood Hall in his honor.
Isherwood was married in Baltimore to Mrs.
AnnaHansine (Munster) Ragsdale, shortly after
the death in 1848 of her first husband.

[G. W. Baird, in Jour. Am. Soc. of Naval Engineers,
Aug. 1915; F. G. McKean, in the same journal, Nov.
1915; R. H. Thurston, in Cottier's Mag. (N. Y.), Aug.
1900; B. F. Isherwood, "The Sloop-of-War Wampa-
noag," Ibid., Aug. and Sept., 1900; R. H. Thurston, A
Manual of the Steam-Engine (1891); L. R. Hamersly,
The Records of Living Officers of the U. 5*. Navy and
Marine Corps (7th ed., 1902) ; Who's Who in America,
1914-15; Trans. Am. Soc. Mech. Engineersf vol.
XXXVII (1915) ; Army and Navy Jour.t June 26, July
3, iQiS; N. Y. Times, June 20, 1915.] F. A.T.

ISOM, MARY FRANCES (Feb. 27, 1865-
Apr. 15, 1920), librarian, the daughter of Dr.
John Franklin Isom and Frances A. (Walter)
Isom of Cleveland, Ohio, was born in Nashville,
Tenn. She attended Wellesley College (1883-
84), But on account of failing health w'as unable
to continue her college course. In 1899, after the
death of her father, she determined upon library
work as a career. She then entered the Pratt In-

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