Reginald Aldworth Daly (May 19, 1871 – September 19, 1957) was a Canadian

geologist A geologist is a scientist who studies the structure, composition, and History of Earth, history of Earth. Geologists incorporate techniques from physics, chemistry, biology, mathematics, and geography to perform research in the Field research, ...

. He is best known for being one of the first proponents of the giant-impact hypothesis of the formation of the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

Biography

Reginald Daly was educated at the University of Toronto, where geologist A.P. Coleman persuaded him away from teaching mathematics and into Earth Sciences. He obtained his PhD at

Harvard Harvard University is a private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of higher lear ...

, and did postgraduate work in Germany and France. After working as a field geologist for the International Boundary Commission, he was a professor, and headed the Department of Geology at Harvard University from 1912 until 1942. Daly was president of The Geological Society of America in 1932. For the Boundary Commission, working in six field seasons, Daly mapped the border from the Pacific Ocean to the Great Plains, a rugged swath long and wide – an area of about . He documented the geology alone, but had the help of one field assistant and numerous wranglers and porters. He collected 1,500 rock specimens and made 960 thin sections, using a German polishing technique he learnt as a student. The project also included 1,300 photographs, dozens of lake soundings, stratigraphic and structural mapping, petrology, and morphology. In 1912, he filed his final report with the

Geological Survey of Canada The Geological Survey of Canada (GSC; , CGC) is a Canadian federal government agency responsible for performing geological surveys of the country developing Canada's natural resources and protecting the environment. A branch of the Earth Science ...

, a massive 3-volume tome he called ''North America Cordillera: Forty-Ninth Parallel.'' This work along the 49th parallel led him to formulate a theory of the origins of

igneous rocks Igneous rock ( ), or magmatic rock, is one of the three main Rock (geology)#Classification, rock types, the others being sedimentary rock, sedimentary and metamorphic rock, metamorphic. Igneous rocks are formed through the cooling and solidifi ...

, and later publish his seminal work ''Igneous Rocks and Their Origin'' in 1914. According to Daly's biographer, James Natland, Daly was an early proponent of Arthur Holmes and Alfred Wegener's

continental drift Continental drift is a highly supported scientific theory, originating in the early 20th century, that Earth's continents move or drift relative to each other over geologic time. The theory of continental drift has since been validated and inc ...

theory. Daly summarized his ideas in his 1926 book, ''Our Mobile Earth,'' which included on the title page small print adopted from

Galileo Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...

: '' E pur si muove''. Daly's theory on continental displacement was based partly on the idea that after the Moon was ejected from the Earth, continental movement was an inevitable part of rebalancing the planet; he also suggested that continental material accruing near oceans eventually slips, and forces continents to creep along. He expanded this notion in ''Strength and Structure of the Earth,'' in 1940, where Daly anticipated aspects of

plate tectonics Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...

, including introduction of a " mesospheric shell" and a slippery vitreous basaltic substratum. Daly also proposed the impact theory of lunar creation in 1946, which countered two prevailing notions: George Darwin's hypothesis that the Moon spun out of the primordial Earth due to centrifugal force; and, another fashionable theory that the Moon was a captured wayward asteroid. Daly applied Newtonian physics to make his point, which was later validated. His doctoral students included the Canadian geologist Norman L. Bowen, who, based on experiments and observations of natural rocks, summarized the order of crystallization of common silicate minerals from typical

basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% ...

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

undergoing fractional crystallization, now known as Bowen's reaction series.

Family

In 1903, Daly married Louise Porter Haskell, daughter of Alexander Cheves Haskell and Alice Van Yeveren, and elder sister of Mary Elizabeth Haskell. After their marriage, Louise accompanied Daly on his travels, and in the field, as an assistant. She did much of the work in preparing and editing his manuscripts and books, and Daly's 1914 book on 'Igneous Rocks and their Origin' is dedicated to her; his "inspiring fellow worker".

Awards

In 1909, Daly was elected a member of the

American Academy of Arts and Sciences The American Academy of Arts and Sciences (The Academy) is one of the oldest learned societies in the United States. It was founded in 1780 during the American Revolution by John Adams, John Hancock, James Bowdoin, Andrew Oliver, and other ...

. He was elected to the

American Philosophical Society The American Philosophical Society (APS) is an American scholarly organization and learned society founded in 1743 in Philadelphia that promotes knowledge in the humanities and natural sciences through research, professional meetings, publicat ...

in 1913 and the United States

National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...

in 1925. Daly was awarded the Penrose Medal in 1935, the Wollaston Medal in 1942 and the William Bowie Medal in 1946. In 1950 he became foreign member of the Royal Netherlands Academy of Arts and Sciences. The potassium zirconium silicate mineral dalyiteDalyite
/ref> and craters on

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

and the

are named in his honor. His Cambridge, Massachusetts, house (the Reginald A. Daly House) is now a

National Historic Landmark A National Historic Landmark (NHL) is a National Register of Historic Places property types, building, district, object, site, or structure that is officially recognized by the Federal government of the United States, United States government f ...

References

Bibliography

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External links