Background

Henry Augustus Rowland was born on November 27, 1848, in Honesdale, Pennsylvania, the descendant of a long line of clergymen. He was the son of Henry Augustus Rowland, a Presbyterian pastor of a local church, and Harriette Heyer, the daughter of a New York merchant.

Education

In the spring of 1865, Rowland enrolled at the Phillips Academy in Andover, evidently as a first step toward Yale and the ministry; but he had been an avid chemical and electrical experimenter as a boy, and he wanted to study engineering. In the fall of 1865 he went to the Rensselaer Polytechnic Institute, where, after developing a distaste for a career in the business world, he resolved to devote himself to science. In 1870 he graduated with a degree in civil engineering.

Career

After his graduation with a degree in civil engineering in 1870, Rowland then spent a year as a railroad surveyor and another year as a teacher at the College of Wooster in Ohio. In 1872 he returned to Rensselaer as an instructor of physics.

Rowland’s first major research was an investigation of the magnetic permeability of iron, steel, and nickel. In order to determine this quantity, he set up toroidal transformers made of each of the three metals in question, broke or reversed the direct current in the primary windings, and measured the charge that flowed in the secondary circuit. Plotting the permeability against what he thought was the induced magnetic field, B, for each of the metals, Rowland found that a general mathematical function could be fitted to all the curves; but by using the toroidal arrangement, he had actually measured ΔB rather than B. His data were distorted by effects of hysteresis unknown to him, and it is clear from modern theories of ferromagnetism that his mathematical function had no physical significance. Rowland had proved that - contrary to the assumption then common in the literature on ferromagnetism - magnetic permeability varied with the “magnetizing force,” H and, hence, with B. His work on the subject won the praise of Maxwell and established his reputation as one of the most promising young experimental physicists in the United States.

In 1875 Rowland accepted the chair in physics at the new Johns Hopkins University and went to Europe for a year to inspect various laboratories and purchase apparatus. He traveled widely, discussed contemporary physics with many leading practitioners of his discipline, including Maxwell, with whom he became good friends, and Helmholtz, in whose laboratory he spent four months. Rowland spent about $6,000 on apparatus for the Hopkins physics laboratory, emphasizing equipment suited for research rather than for teaching demonstrations. By the late 1870s the Hopkins facility was far better equipped than any other American or even many European laboratories. In part because of his European trip, Rowland kept in touch all his life with developments in physics abroad, which was unusual for an American physicist of his day. He regarded himself as midway between an experimental and mathematical physicist and often tried to focus his experimental efforts on problems of theoretical import.

In 1868, stimulated by his study of Faraday’s Electrical Researches, Rowland conceived an experiment to test whether the magnetic effect produced by the electric current was the direct result of charge moving through space or of some interaction between the current and the conducting body. Performing the experiment while in Helmholtz’s laboratory, Rowland used a charged vulcanite disc with an astatic needle suspended above it to register magnetic effects. He found no magnetic effects in the arrangement for the interactive case, in which the charge was held stationary while the disc was made to rotate. But he did detect magnetic effects when the charge was allowed to rotate with the disc, and the motion of the astatic needle correlated with the rotational sense of the current. Though not decisively in favor of one or another of the prevailing electrical theories, Rowland’s experiment was the first, as Helmholtz reported to the Berlin Academy of Science, to demonstrate that the motion of charged bodies produced magnetic effects.

Like his studies of permeability, Rowland’s subsequent work was characterized by meticulous attention to experimental detail and remarkable mechanical ingenuity. In the late 1870’s he established an authoritative figure for the absolute value of the ohm. At the opening of the 1880s, he painstakingly redetermined the mechanical equivalent of heat and conclusively showed that the specific heat of water varied with temperature. Then Rowland turned to the work for which he is best known, the invention and ruling of the concave spectral grating.

The range, resolving power, and accuracy of a grating was determined respectively by the number, density, and regularity of its rulings. Lewis Rutherfurd, an amateur astronomer in New York City, had managed to rule up to two square inches of metal with thirty thousand lines per linear inch, but his gratings were inaccurate. Rowland recognized that to make a grating of highly uniform line-spacings, one needed an exceedingly regular drive screw in the ruling engine. He found that he could manufacture a nearly perfect drive screw from a roughly cut screw simply by grinding it in an eleven-inch-long nut which, split parallel to its axis, was clamped over the screw. With the problem of the screw overcome, Rowland could rule up to forty-three thousand lines per inch on more than twenty-five square inches of metal and, hence, construct gratings of unprecedented accuracy and resolving power.

Rowland saw numerous advantages in ruling his gratings on a spherically concave grating rather than on a flat surface. Since such gratings were self-focusing, they eliminated the need for lenses, in which the glass absorbed infrared and ultraviolet radiation. More importantly, the optical properties of a concave grating permitted a vast simplification in the observation of spectra. Consider a circle drawn tangent to the inner face of the grating with a radius equal to half its curvature. Wherever on the circle, the source was placed, its spectrum would come to a normal focus at an eyepiece placed at the opposite end of a diameter from the grating. If the eyepiece was fixed at that point, the focus of the apparatus had to be set only once. By moving the source, one could quickly read off the wavelengths of numerous spectral lines from a scale on a chord of the circle, easily photograph the spectrum of one element superimposed on that of another element, or reliably determine line intensities even in the infrared region.

The concave grating reduced the work of days to a few hours, and Rowland sold over 100 of them at a cost to physicists throughout the world. In the 1880’s Rowland remapped the solar spectrum; his wavelength tables, which were ten times more accurate than their best predecessors, became the standard for over a generation. At the Paris Exposition of 1890, his gratings and map of the solar spectrum received a gold medal and a grand prize. Rowland’s numerous other professional honors included an appointment as a delegate of the United States government to various international congresses on the determination of electrical units. He became a foreign member of the Royal Society of London and the French Academy of Sciences and was elected to the National Academy of Sciences, which awarded him its Rumford and Draper medals. He was a founder and also the first president of the American Physical Society.

In 1883, as vice-president of the American Association for the Advancement of Science, Rowland delivered a celebrated address, “A Plea for Pure Science,” in which he disparaged technological invention and called upon his fellow countrymen to do more to foster basic research. But near the end of his life, Rowland became an inventor himself.

After 1890, it was discovered that Rowland had diabetes, and, eager to assure the future of his family, he worked on the development of a multiplex telegraph. Although technically successful, the system had not proved to be feasible commercially by the time of his death. In accordance with his express wish, Rowland’s ashes were interred in the wall of the basement laboratory, where the engine with which he ruled his gratings was housed.

Achievements

• 

  Rowland's major achievement was in becoming one of the greatest physicists of the nineteenth century who also became highly reputable on the international level. His determination to the mechanical equivalent of heat was one of his most important investigations. His study of the magnetic properties of iron led to entirely new conceptions of magnetism. Among his greatest contributions was the improvement of thermometric and calorimetric methods, he also redetermined the mechanical equivalent of heat and redetermined the standard value of electrical resistance, the Ohm.
  
  He not only made an eye study of the spectrum but also applied photographic methods. Rowland investigated the solar spectrum and the arc spectra of various elements and carried on many researches in allied fields. His work on alternating currents and their application has also been of importance. One of his last investigations resulted in the development of a system of multiplex telegraphy based on the use of synchronous motors, for which he received a gold medal from the Paris Exhibition. The results of his labors may be found in the elaborate Photographic Map of the Normal Solar Spectrum (1888) and the Table of Solar Wave-Lengths (1898).
  
  The National Academy of Sciences awarded Rowland the Henry Draper Medal in 1890 for his contributions to astrophysics. He won the Matteucci Medal in 1895. Also, in 1899 Rowland became one of the founders of the American Physical Society and served as its first president, ruling until his death in 1901.

Works

More photos

• book

  • Preliminary Table of Solar Spectrum Wave-Lengths

    (Part 1)

    1898
  • On a Table of Standard Wave Lengths of the Spectral Lines 1896
  • The Physical Papers of Henry Augustus Rowland 1903
  • On the Mechanical Equivalent of Heat: With Subsidiary Researches on the Variation of the Mercurial From the Air Thermometer, and on the Variation of the Specific Heat of Water 1880
  • Elements of Physics 1900
  • Arc-spectra of vanadium, zirconium, and lanthanum 1898
  • On the Electromagnetic Effect of Convection-currents 1889
  • Report Of The Electrical Conference At Philadelphia 1884
  • The highest aim of the physicist 1899
  • Research on the absolute unit of electrical resistance 1878

• Invention

  • Dividing engine for ruling gratings for spectrum anayzers

    (Rowland invented a ruling engine that achieved unpreceden...)

    1896

Religion

Henry Rowland came from a long line of sturdy Protestant theologians. His great-grandfather had spoken from his pulpit against foreign oppression so zealously that during the War for Independence, when a British fleet invested Providence, he had to flee the city. Henry Rowland was expected to go into the ministry, but he preferred to work on home-made experiments.

Views

Rowland was always interested in the mechanism of electric currents, as is shown by many of his early experiments, and it was in the course of testing some of his deductions as to the nature of a current that Dr. E. H. Hall was led to the discovery of what is called the "Hall Effect".

The cause of terrestrial magnetism was another problem which attracted Rowland from early youth; he persistently believed that terrestrial magnetism is in some way connected with the rotation of the earth, and one of his last experiments was an attempt to discover whether a piece of matter in rapid rotation would give rise to a difference of potential. In the field of measurements, he obtained values that are still accepted for the mechanical equivalent of heat (this he considered one of his principal achievements), the ohm, the ratio of the electric units and the wave-lengths of various spectra.

Quotations: “There is no such thing as absolute truth and absolute falsehood. The scientific mind should never recognise the perfect truth or the perfect falsehood of any supposed theory or observation. It should carefully weigh the chances of truth and error and grade each in its proper position along the line joining absolute truth and absolute error.”

Membership

Rowland became a foreign member of the Royal Society of London in 1899. He was a member of the French Academy of Sciences and was elected to the National Academy of Sciences. He was also a founding member of the American Physical Society and between 1899 and 1901 served as the first president of the Society.

• 

  Royal Society of London , United Kingdom

  1899 - 1901

Personality

Physical Characteristics: At the end of his life, Rowland developed a bad case of diabetes that became fatal to him, and from which he died on April 16, 1901.

Interests

• Photography, fishing, sailing, fox-hunting

Connections

On June 4, 1890, Rowland married Henrietta Troup Harrison of Baltimore, who with two sons and one daughter survived him.

Father:

Henry Augustus Rowland

Mother:

Harriette Heyer

She was the daughter of a New York merchant.

Wife:

Henrietta Troup Harrison

teacher:

Hermann von Helmholtz

Rowland studied physics under Hermann von Helmholtz at Berlin, and carried out well-known research on the effect of an electrically charged body in motion, showing it to give rise to a magnetic field.

associate:

James Maxwell

Maxwell appreciated the value of Rowland’s experiments and had them published in the Philosophical Magazine. Although his work was known in Europe, Rowland was mainly overlooked by fellow American scientists.

colleague:

Daniel Coit Gilman

July 6, 1831 – October 13, 1908, an American educator and academic. Gilman was instrumental in founding the Sheffield Scientific School at Yale College, and subsequently served as the second president of the University of California, Berkeley, as the first president of Johns Hopkins University, and as founding president of the Carnegie Institution.

Rowland's quest for a place to do research ended suddenly in 1875 when he met Daniel Coit Gilman. Gilman was assembling a faculty for the newly endowed Johns Hopkins University, which was to be America's first true research institution, complete with graduate students, on the German model. Rowland joined happily and was sent on a tour of Europe to study laboratories and buy instruments.

References

• The Golden Age of Science
  1966
• Dictionary of Scientific Biography Volume 11
  1975
• The Command of Light: Rowland's School of Physics and the Spectrum
  2000
• Science in Nineteenth-Century America: A Documentary History
  1985