MAYER, Brantz, author, born in Baltimore, Maryland, 27 September. 1809: died there, 21 March, 1879. He was educated at St. Mary's college, Baltimore, and studied law during a long voyage to the East in 1827-'8. On his return home he entered the law department of the University of Maryland, and was admitted to the bar in 1829. After practising for several years he visited Europe in 1833, and in 1843 was appointed secretary of legation in Mexico. When he returned home he published his first work, "Mexico as it Was, and as it Is" (Philadelphia, 1844), which was accused of unfairness and gave rise to animated controversy. In the winter of 1844 Mr. Mayer founded the Maryland historical society, the original object of which was "the collecting the scattered materials of the early history of the state, and for other collateral purposes." From a membership of twenty it has steadily increased to the present membership of two hundred, including many professional men as well as merchants. During the civil war Mr. Mayer was an active Unionist, and in 1861 was appointed president of the Maryland Union state general committee, and did much to aid the National cause. In February, 1863, he was appointed a paymaster in the United States army, and was retained in the service after the close of the war. He served in Maryland, Delaware, and California until his sixty-second year, when he was retired from active service with the rank of colonel. Besides the work mentioned above, he published "Mexico. Aztec, Spanish, and Republican" (2 vols., Hartford, 1851) ; "Captain Canot, or Twenty Years of an African Slaver," founded on fact (New York, 1854); "Observations on Mexican History and Archaeology" in "Smithsonian Contributions to Knowledge" (Washington, 1856); "Mexican Antiquities" (Philadelphia, 1858); "Memoir of Jared Sparks" (1867); and "Baltimore as it Was and as it Is" (1871), and he contributed to the papers of the State historical society "The Journal of Charles Carroll during his Mission to Canada" (1844), and "Tah-gali-jute, or Logan and Captain Michael Cresap" (1851; Albany, 1867).--His nephew, Frank Blackwell, artist, born in Baltimore, Maryland, 27 December, 1827. He studied under Gleyre and Brion at Paris, and his studio is now (1888) at Annapolis, Maryland lie exhibited at the Paris salon, and was given a medal at Philadelphia in 1876 for his "Continentals" and "Attic Philosopher." Mr. Mayer has made a special study of Indian types and character in the west. Among his works are " The Feast of Mondawmin " (1857) ; " Doing and Dreaming" (1858); " The Nineteenth Century " (1869): " Annapolis in 1750" (1876) ; "Talking Business, 1750" (1879); "Crowning a Troubadour" (1885); and "Treaty of Traverse des Sioux, Minnesota" (1886). He has also produced portraits in crayon and oil, including a crayon head of Chief-Justice Taney, and has contributed articles, with illustrations, to " Harper's " and the " Century" magazines.--Frank Black-well's brother, Alfred Marshall, physicist, born in Baltimore, Maryland, 13 November, 1836, was educated at St. Mary's college, Baltimore, but left in 1852 to enter the workshop and draughtingroom of a mechanical engineer, where he remained two years, acquiring a knowledge of the use of tools, mechanical drawing, and methods of constructing machines, he then ", spent two years in obtaining a thorough knowledge of analytical chemistry by laboratory practice. In 1856 he was called to the chair of physics and chemistry in the University of Maryland, and in 1859-'61 he held a similar post in Westminster college, Missouri In 1863-'4 he studied physics, mathematics, and physiology in the University of Paris, and on his return he filled successively chairs in Pennsylvania college, Gettysburg, and Lehigh, university, Bethlehem, during 1865-'70. At the latter institution he had charge of the department of astronomy, and superintended the erection of an observatory. He had charge of the expedition that was sent to Burlington, Iowa, under the auspices of the United States nautical almanac office to photograph the solar eclipse of 7 August, 1869, and made forty-one perfect photographs. In 1871 he accepted the professorship of physics in Stevens institute of technology, Hoboken, New Jersey, which chair he still holds, His scientific researches since that time have been principally published in the "American Journal of Science" under the title of " Researches in Acoustics" (1871-'5). These include experiments showing that the translation of a vibrating body causes it to emit waves differing in length from those produced by the same vibrating body when stationary; a method of detecting the phases of vibration in the air surrounding a sounding body, leading to his invention of the topophone; mode of measuring the wave-lengths and velocities of sound in gases, resulting in the invention of an acoustic pyrometer; the determination of relative intensities of sound; five new methods of sonorous analysis for the decomposition of a compound sound into its elementary tones; the discovery that the fibrils of the antennae of the male mosquito vibrate sympathetically to notes which have the range of pitch of the sounds given out by the female mosquito; and the determination of the laws of vibration of tuning-forks, especially in the direction of the bearing of these laws on the action of the chronoscopes that are used in determining the velocities of projectiles. He contributed to the "Scientific American Supplement" during 1876-'8 an extensive series of papers "On the Minute Measurements of Modern Science." His other memoirs include "On the Effects of Magnetization" in changing the dimensions of iron and steel bars (1873); "Method of Investigating the Composite Nature of the Electric Discharge" (1874) ; "Experiments with Floating Magnets" (1878) ; "Acoustic Repulsions" (1878); "A New Spherometer" (1886) ; "On the Coefficient of Expansion and Diathermancy of Ebonite (1886); and "On Measures of Absolute Radiation" (1886). Prof Mayer received the degree of Ph.D. from Pennsylvania college in 1866. He is a member of scientific societies, and in 1872 was elected to the National academy of sciences. In 1873 he was one of the associate editors of the "American Journal of Science," but after a year's service withdrew on account of failing eyesight. Besides numerous articles in his special branches of inquiry contributed to cyclopaedias and journals, he has published "Lecture Notes on Physics" (Philadelphia, 1868) ; "The Earth a Great Magnet" (New Haven, 187'2) ; "Light" (New York, 1877) ; "Sound" (1878) : and " Sport with Gun and Rod in American Woods and Waters" (1883).