Ralph Howard Fowler (1889 - 1944) was a British theoretical physicist and physical chemist who was a top class scientist in many areas, mainly in statistical mechanics, quantum mechanics, nuclear physics, condensed matter physics and theoretical astrophysics. He made important contributions to statistical mechanics and theoretical astrophysics on the Nobel Prize level.
S. Chandrasekhar in his obituary article "Ralph Howard Fowler", THE ASTROPHYSICAL JOURNAL, vol.101, no 1 (1945) wrote: "We owe to Fowler some of the very fundamental ideas in modern astrophysics; and his work, characterized by a rare combination of physical insight and mathematical precision, shows what theoretical astrophysics at its best can be".

Ralph H. Fowler was educated at Winchester and at Trinity Coledge, Cambridge, where he was elected to a prize fellowship for research in pure mathematics. After completion of his degree, Ralph took to researching pure mathematics. His adeptness and insight won him a Trinity Fellowship in October 1914. However, World War I had just broken out and he obtained a commission in the Royal Marine Artillery. He worked as a mathematician for ballistics work in a Group n Portsmouth, where he was an Assistant Director. Fowler recruited a long list of able mathematicians to join the group. Fowler's mathematical ability led the group to a number of important works. Many were published in journals including two now classic papers that appeared in the Philosophical Transactions of the Royal Society that were to have a profound impact on the field of ballistics both in Britain and in North America, particularly in World War II.
Fowler apparently was active in both the experiments as well as the laborious paper-writing. His work in this field led him, in particular, to consider wind structure and temperature structure at high altitudes which could have been the catalyst for his later interest in thermodynamics and statistical mechanics. For his ballistics work, Ralph Fowler was awarded the OBE in 1918.
In 1919 Fowler left the service and returned to Trinity, though he was to have a part in the newly formed Ordnance Board during the Second World War later on. This was when Fowler came under the influence of Lord Rutherford who had just been appointed Cavendish Professor. The two became very good friends and Fowler was eventually appointed College Lecturer in Mathematics in 1920. Here he jumped into a variety of mathematical problems and eventually began moving to more recent problems in mathematical physics including work on various kinetic theories of gases, again leading him toward thermodynamics and statistical mechanics.
In 1921, Ralph married Eileen, the only daughter of Lord Rutherford, Ralph's good friend and colleague at Cambridge. The two were to have four children in the following nine years with Eileen dying just after the birth of the last.

In 1922, Ralph Fowler became a Proctor at Cambridge which, being a Marine, he was well-suited for, finding himself chasing after undergraduates frequently and, on one occasion, injuring himself doing so. It was also in 1922 that Ralph began what would be his most seminal work. It began as a collaboration with C G Darwin (another of the famous Darwin clan). The two began working on the problem of the partition of energy, inspired by works of Ehrenfest and Trkal. Having developed a new technique for approaching physical chemistry through statistical mechanics, the two, and later Fowler alone, justified a number of formulae and calculations performed by the likes of Saha, Lindemann, and Chapman.
In 1922-23, Ralph established the validity of the dissociation formula for high temperature ionization. In early 1923, Ralph along with E A Milne, wrote a seminal work on stellar spectra, temperatures, and pressures. This work continued in a series of papers through the 1920s leading to the Adams Prize of the University of Cambridge in 1923-24 and was published in 1929 as the seminal volume, Statistical Mechanics, which had a second edition, minus the astrophysical applications, published in 1936. In 1939 a successor volume, entitled Statistical Thermodynamics, was co-authored and published with E A Guggenheim.
1926 marked the publication of his most seminal individual paper which linked the gaseous degenerate state (obeying quantum statistics, co-discovered by P A M Dirac, who was introduced to quantum theory by Fowler himself) to white dwarf stars. It is rumored that he was annoyed that he did not, at the same time, apply Fermi-Dirac statistics to conductors, something later done by Sommerfeld.

Working closely with his father-in-law, Lord Rutherford, he examined a number of interesting problems and delivered the 1935 Bakerian Lecture on specific heats of crystals and the 1934 Liversidge Lecture on the heavy isotope of hydrogen. In 1925 he was elected as a Fellow of the Royal Society and became a Fellow at Winchester in 1933. In 1936 he was awarded one of the Royal Medals and was appointed as Director of the National Physical Laboratory in 1938, though he was unable to take up the post due to ill health. According to Milne, the transformation from pure mathematician prior to World War I to physicist, engineer, and administrator by Word War II was nothing short of astonishing and a great tribute to Fowler's ability in practical matters.
Fowler's range of interests kept him going throughout the next two decades as he produced papers on spectroscopy, physical chemistry, what is now known as condensed matter physics (or solid state physics), and magnetism in materials. He eventually took up a post in the Cavendish Laboratory at Cambridge and, in 1932, he was elected to the newly created Plummer Chair of Theoretical Physics.

It must be said that Sir Ralph Fowler was a brilliant physicist. But it may be for his influence upon others that he is best known. In fact, no less than fifteen Fellows of the Royal Society and three Nobel Laureates were supervised by Fowler between 1922 and 1939. The total number supervised during this time was a staggering sixty-four giving him an average of eleven research students at any given time. One might be led to believe that this did not allow for any depth of relationship to form between him and his students. However, this was far from the truth of the matter. Those who studied under Fowler had a tremendous admiration for him. In particular, E A Milne was especially taken by the man whom he fondly referred to as "the kind of man you can still remain friendly with, even when he has sold you a motor-bike; it is not possible to say more" and whom he called a "prince amongst men". (MacTutor Biography)

Darwin–Fowler method:
Darwin–Fowler method was developed by Ch. Darwin and R. Fowler in 1923.
Darwin–Fowler method is a method for the derivation of the Gibbs canonical and grand canonical distributions from the micro-canonical distribution. One considers an ensemble of similar statistical systems which form a closed system on the whole, and its characteristic distribution function is summed over the microscopic states of all the systems in the ensemble except for one. It is assumed that the number of systems in the ensemble tends to infinity (if the number of particles in each one of the systems in the ensemble is large but finite); this makes it possible to use the saddle point method in computations. The use of this procedure to determine several common characteristics of statistical systems and to compute their concrete characteristics yields the same results as the method based on the Gibbs canonical distributions.
References:
1.Charles Galton Darwin and Ralph H. Fowler "On the partition of energy", Philosophical Magazine 44 pp. 450-479 (1922);
2.Charles Galton Darwin and Ralph H. Fowler "On the partition of energy - Part II Statistical principles and thermodynamics", Philosophical Magazine 44 pp. 823-842 (1922);
3.Charles Galton Darwin and Ralph H. Fowler "Fluctuations in an assembly in statistical equilibrium", Proceedings of the Cambridge Philosophical Society 21 pp. 391-404 (1923);
4.Charles Galton Darwin and Ralph H. Fowler "Some refinements of the theory of dissociation equilibria", Proceedings of the Cambridge Philosophical Society 21 pp. 730-745 (1923);
See also: K. Huang, "Statistical mechanics" , Wiley (1963)

In 1928 at Cambridge, R. Fowler in collaboration with L.W. Nordheim have worked on the phenomenon of cold electron emission from metals. They formulated a theory on the basis of electron cyclotron tunneling. This theory was called the Fowler–Nordheim theory. The Fowler–Nordheim tunneling was observed in nonconducting thin films, for example, SiO2 films. The Fowler–Nordheim model is still widely used and cited. For example, for calculation of electronic high-vacuum devices (relativistic diodes), electron emission was described by quantum mechanical Fowler–Nordheim equations. Also, when a new method for the manufacture of graphite nanotubes was proposed it happened that during analysis of devices with graphite nanotube emitters (integrated with a metallic anode), secondary emission was best analyzed within the Fowler–Nordheim model, which made it possible to considerably improve the fabrication process.
For more details on the works of L.W. Nordheim see Review article:
A.L.Kuzemsky, Works of D.I. Blokhintsev and Development of Quantum Physics
Physics of Particles and Nuclei, 2008, vol. 39, Issue 2, pp.137-172.
( http://theor.jinr.ru/~kuzemsky/preprints/Blokhintsev08.pdf) (in English).
Russian version is available at:
Physics of Elementary Particles and Atomic Nuclei, 2008, vol. 39, Issue 1, pp.5-81.
http://theor.jinr.ru/~kuzemsky/preprints/DIBREV08.pdf.

Books by R. Fowler:
* R. Fowler, E. Guggenheim, "Statistical thermodynamics" , Cambridge Univ. Press (1960)
* R. Fowler, Statistical Mechanics. 2nd ed Cambridge Univ. Press (1966)

There are a few places where the biography of Ralph H. Fowler can be found.

Wikipedia electronic Encyclopedia(http://en.wikipedia.org/) , an article Ralph H. Fowler.
Additional Material see in MacTutor BIOGRAPHY of R.H. FOWLER.