FOTHAD
156
FOUCAULT
partments of Virginia and North Carolina were as-
signed to him from July to November, 1863, and then
that of Ohio, which he had to relinquish, owing to in-
juries received by a fall from his horse. He next
aided Sherman in the reduction of Charleston, and for
gallant services in the capture of Savannah was bre-
veted brigadier-general in the regular army. Dur-
ing 1S65-6 he was in command of the Department of
Florida, and then superintended various river and
harbour improvements. In the harbours of Boston
and Portsmouth he conducted, with great ability and
success, important submarine operations, an experi-
ence which adtled the value of direct experience to his
work on "Submarine Blasting in Boston Harbor"
(New York, 1869) and his articles in various periodi-
cals on engineering subjects, which received high pro-
fessional approval.
Pilot (Boston, Sept., 1874), files; Cyclopaedia of American Biography, II, s. v.
Thomas F. Meehan.
Fothad, Saint, surnamed na Canoine (of the Canon), a monk of Fahan-Mura, County Donegal, Ire- land, at the close of the eighth century. He became bard, counsellor, and tutor to Aedh Oirnidh (the digni- fied), Ard Righ (Head King) of Ireland, who ruled from 794 to 81S. He is specially venerated in the Irish Church from the fact that, in 804, when he ac- companied King Aedh in his expedition against the Leinstermen, he obtained from that monarch exemp- tion of the clergy forever from military service. His literary gifts were so highly thought of that St. Aengus submitted liis " Felire " to him for his approval, and, in return, St. Fotliad presented St. Aengus with a copy of his " Remonstrance ", addressed to King Aedh, pro- testing against the conscription of ecclesiastics. This " Remonstrance ", which was really a rhymed judicial opinion, was known as a canon or decree, and hence St. Fothad was ever after called "Fothad na Canoine". It commences thus: " The Church of the living God let her alone, waste her not ".
O'Hanlon, Lives of the Irish Saints (Dublin, s. d.); Hyde, hit. Hist, of Ireland (X'Ondon, 1901); Healy, Ireland's Ancient Schools and Scholars (Dublin, 1902); O'Ccrhy, Lectures (Dub- lin, 1861) ; Mathew, The O'Neills of Ulster (Dublin, 1907).
W. H. Grattan-Flood.
Fouard, Constant, ecclesiastical writer; b. at Elbeuf, near Rouen, 6 Aug., 1837; d. at his native place, 3 Dec, 1903. The whole of his early life was a preparation for the work on which his fame rests. He studied the classics at Boisguillaume, philosophy at Issy (1855-1857), and made liis theological studies at St-Sulpice, Paris (1857-61). Among his profes- sors at Paris were Abbe John Hogan, who remained throughout life the inspirer and mentor of his studies, and Abb^ Le Hir, who initiated !iim and his fellow- disciple Vigouroux into Biblical science, to which they devoted their Uves. He was ordained priest in 1861 and entered the " Solitude ", the novitiate of the Sulpi- cians, but left on account of illness after several months without joining their society. He taught for some time at Boisguillaume, then pursued the study of classics at the college of Saint Barbara, Paris, obtained the degree of Licentiate in Letters, 1867, and resumed the teaching of classics at Boisguillaume, taking the class of rhetoric, 1867-1876. His piety drawing him to sacred sciences, he was appointed by the State (1876) to the chair of Holy Scripture in the faculty of theology at Rouen; he continued, however, to reside at Boisguillaume and to share in the duty of governing the student-body.
Honours came to him : he was made doctor of theo- logy (1877), canon of the catliedral of Rouen (1884), and member of the Biblical Commission (1903). His ecclesiastical science, his piety, his spiritual wisdom were continually at the service of religion in his native diocese. For the benefit of his studies he travelled in Palestine, Syria, Greece, and Italy. The Faculty of
Theology being suppressed about 1884, his teaching
ceased. His writings are: "La Vie de N-S J^sus-
Christ" (1880); "Saint Pierre et les premieres ann^es
du Christianisme " (1886) ; " Saint Paul, ses Missions "
(1892); "Saint Paul, ses dernieres annfies" (1897);
" Saint Jean et la fin de I'age apostolique " (posthu-
mous, 1904). The dates witness, incidentally, to the
extremely painstaking character of his labours. All
these books form part; of one grand work, " Les Or-
igines de I'Eglise", which Fouard wrote as an answer
to the presentation of the same subject by Renan, who
like himself had been a pupil of Le Hir. Each succes-
sive book of the Aljb^ Fouard immediately gained a
wide popularity and was translated into nearly all the
languages of Europe.
_ His work is esteemed for the interest of its narra- tives, the purity of its diction, its correctness in doc- trine, its conservative but not reactionary critical viewpoint, its breadth and accuracy of erudition, and for its evidently sincere piety, the manifestation of a good and gentle spirit, loving God, delighting in na- ture, and earnestly desiring to do good to men. With one touch of genius, or greater depth of feeling (gifts which were denied him), he might have fused the various elements of his -nTitings into a truly great work. His works are not remarkable in originality of view or acuteness of critical insight, but present, as a whole, a faithful picture of early Christianity, satisfying to the Christian heart. Perhaps his most esteemed books are the two on Saint Paul. The English translation of his writings is exceptionallv well done.
Bulletin des Anciens Sieves de St-Siilpice (Paris. 1904).
John F. Fenlon.
Foucault, Jean-Berthand-Leon, physicist and mechanician, b. at Paris, 19 Sept., 1819; d. there 11 Feb., 1868. He received his early schooling at home and showed his mechanical skill by constructing a boat, a mechanical telegraph, and a working steam- engine. He passed the examinations for the B.A. and began to study medicine. Later, unable to bear the sight of blood, he abandoned medicine and worked for Donn^ as preparator in his course on medical micros- copy. His elementary mathematical and scientific training had been very deficient and he supplemented it as he became interested in invention and experiment. In 1845 he succeeded Donne as scientific editor of the "Journal des D^bats". In 1850 he was awarded the Copley medal, the highest honour of the Royal Society of London, for his work showing the relation between mechanical energy, heat, and magnetism. The posi- tion of physicist of the Paris Observatory was created especially for him in 1855. A member of the Bureau of Longitudes (1862), he was finally elected to the Acad- emy in 1865. Those of Berlin and St. Petersburg, and the Royal Society of London also honoured him.
Foucault worked along several lines. With Fizeau he experimented upon the interference of red rays and their influence on daguerrotype plates, wliile with Regnault he studied binocular vision. We are in- debted to him for the crucial experiment overturning the corpuscular or emission theory of light, defended by Kepler, Newton, and Laplace. Following Arago's suggestion he used the rotating mirror of Wheatstone to determine the difference between the velocities of light in various transparent media. Contrary to the emission theory he found that light travels faster in air than in the denser medium water (17 May, 1850). Light was reflected from a mirror through a tube, con- taining the medium to be studied, to a concave reflec- tor and back again to the mirror. If the mirror was rotated, the image was observed to shift by an amount depending on the speed of light through the particvilar medium in the tube. Exceedingly accurate measure- ments were made of this enormous velocity (about 186,000 miles per second) with an apparatus occupy- ing only twelve feet of space. Foucault invented an
