Born in Memphis, Brown Ayres attended Washington and Lee and transferred to the Stevens Institute of Technology where he received the BS in engineering in 1878. Johns Hopkins granted him a fellowship in physics in 1879–80. By 1888 he had earned the PhD from Stevens. At Stevens, Ayres was especially interested in electricity and became personally acquainted with Thomas Alva Edison and Alexander Graham Bell. He was offered a position with Bell’s fledgling telephone company, but he declined in favor of pursuing an academic career.
In 1880 Ayres accepted the post of professor of Physics and Electrical Engineering at Tulane. He became dean of the College of Technology in 1894 and was vice chairman of faculty and dean of the Academic College in 1900. Continuing his interest in electricity, he served as a member of the Jury of Electricity at the Columbian (1893), Atlanta (1895), and Nashville (1897) Expositions. When the UT trustees were seeking a new president in 1904, Ayres was serving as acting president of Tulane. The trustees elected Dr. C. Alphonso Smith, associate professor of English at the University of North Carolina, to succeed President Dabney. But after visiting the institution in July 1904, Smith declined.
Dabney had written a letter to trustee Edward Sanford recommending Ayres, pointing out that Ayres had been strongly considered for the presidency at Tulane and had recently declined the presidency of the University of Alabama. Ayres was not a stranger to the university. He had been on the faculty of UT’s first (1902) Summer School of the South and had been offered a position with the university the same year.
Ayres served as UT president from 1904 until his death on January 28, 1919. During his administration, the university received its first $1 million appropriation (1917) from the legislature.
Ayres received many honors during his career. He was awarded LLD degrees from Washington and Lee University (1894), South Carolina College (1905), Tulane University (1905), and the University of Alabama (1916). He served as president of the Association of Colleges and Preparatory Schools of the Southern States (1904–5), president of the National Association of State Universities (1909–10), and vice president (having declined the presidency) of the Association of Land-Grant Colleges of the United States. He was a fellow of the American Association for the Advancement of Science and belonged to the American Institute of Electrical Engineers, American Physical Society, Association for the Promotion of Engineering Education, Phi Beta Kappa, and Phi Kappa Phi. He married (1881) Kate Allen Anderson of Lexington, Virginia. The Ayres had three sons and five daughters.