Oldham

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Oldham writes in 1906

…..there remain two important questions to be answered, namely the size of the core and the rate of transmission of the waves in it. As regards the size of the core, we have seen that it is not penetrated by the wave-paths which emerge at 120°; and the great decrease at 150° shows that the wave-paths emerging at this distance have penetrated deeply into it. Now the chord of 120° reaches a maximum depth from the surface of half the radius, and we have seen that the wave paths up to this distance are convex towards the centre of the Earth, so it may be taken that the central core does not extend beyond 0.4 of the radius from the centre.

P 470 Proc. R. Soc. Aug 1906. "Mr R. D. Oldham on the constitution of the Interior of the Earth."

Link to Griesbach

Richard Dixon Oldham was born in Dublin 31 July 1858, one of five sons and a daughter of Louisa Matilda Dixon of Liverpool and Thomas Oldham (1816-78) the first Director of the Geological Survey of India. Louisa and the six children lived at Eldon Place during the 1871 census (with two servants). Richard Oldham studied at Rugby (c.1871-5) where in 1874 at the age of 16 he published his first articles on geology. He attended the Royal School of Mines (c1875-1878) and towards the end of this time he was elected to a science scholarship at Emmanual College, Cambridge. His father returned from India 1876 but died in 17 July1878. He completed the first of three of his father's unfinished articles at the family home in May 1879, a dictionary of geological terms, and it is possible that the two discussed its contents before his father died. At about this time Oldham declined the Cambridge offer in favor of accepting a post as a geologist in India.

In December 1879 he was appointed an officer in the Geological Survey of India, and in early1880 was sent to work with William King. Almost immediately he contracted malaria and later that year was sent to Simla in the Himalaya to recover. Serendipitously a huge landslide occurred at NainTal while he was there and he was able to study it at first hand and to prepare an insightful report on the processes involved. It is probable that he spent some considerable time absorbing all available published materials on Indian Geology, completing his father's unfinished articles during this period of convalescence in 1880. He was subsequently deputed to unravel the complexities of Himalayan stratigraphy but shortly after starting on this he volunteered to join the Manipur/Burma boundary mapping team. He spent Christmas 1881 in Manipur (at the time of the 31December Car Nicobar earthquake) and returned northwards through Assam. In the period 1882-4 he worked first in Simla and then north of Dehra Dun mapping the stratigraphy of the mountains. He had assembled materials for an article on the Car Nicobar earthquake, but only in 1885 was he to visit the Andaman Islands with a Survey of India topographic mapping team. Applying for extended leave following this expedition he chose in August/September to visit Australia, but a bout of malaria curtailed his visit to a three week tour of Newcastle and the Hunter River Valley. While there he examined evidence for glaciation in Late Palaeozoic rocks, a geological process he had become adept at recognising in the lesser Himalaya, and which he was to describe subsequently in the Salt Ranges. In November 1885 he wrote his account of his Australian findings in a camp in Ajmere in Rajasthan where he had been sent to search for coal deposits. In 1886 he left the deserts and travelled to Simla and Ladakh to verify earlier stratigraphical mapping, and on his return was deputed to investigate aspects of Salt Range stratigraphy. In 1889 and for the next two years he lead a team to map the region of Baluchistan between Sibi and Quetta in a quest for oil and coal.

In addition to his bibliography of articles on Indian geology which he compiled in 1888, he published several articles that were outside his immediate field responsibilities. In 1888 he compiled a list of articles on Indian geology. He wrote several articles attempting to reconcile Himalayan geology with the views of Osmond Fisher whose book on the Physics of the Earth was to influence him throughout his career. In 1893, desiring to synthesise Indian geology with modern findings and with the approval of the current direcotr William King, he rewrote the Manual of the Geology of India. In June 1897 while acting as temporary director to King's successor, Griesbach, Calcutta was shaken by the Mw=8.1 Shillong Plateau earthquake, which was to change his scientific career. The study of the earthquake dominated his activities in 1898 which included a research visit to London libraries. His published report in 1899 is a prelude to his most important contributions in seismology, which were destined not to occur in India.

Although Oldham joined as assistant Superintendent in 1878, was a Deputy Superintendent in 1886, Superintendent in 1893, and Officiating Director in 1897 he never succeeded his father as Director of the Geological Survey of India, a position which passed from C.L Griesbach to T.H. Holland in 1903. Oldham's last fieldwork in India (21 March-16 October 1903) was to examine the glacial and physical history of the Indus Valley in SE Kashmir. On 3 July 1899 at age 40 he was granted 18 months furlough and travelled to Sri Lanka and to the UK where he lived briefly with his sister Dorothea at 4 Gyllyngvase Terrace, Falmouth, apparently extending his furlough at least until 31 March 1901. He left the Survey of India 2 Nov 1903 using 6 months of leave prior to official retirement 1 May 1904, 9 years before mandatary retirement. According to Davison (1936) he resigned in 1903 and returned to England "partly due to ill health" but the precise timing of his departure to avoid overlap with Holland suggests that it is possible that he was dissappointed at having been passed over by a relative newcomer 11 years his younger.

Back in England he focussed his attention on the interpretation of seismograms leading to the first correct identification of different types of seismic wave produced by earthquakes. This quickly lead him to realize that the Earth had a core and that seismic waves could be used to determine the depth of earthquakes, and their cause. Following a series of pioneering articles on seismicity he turned his attention to gravity and the interpretation of Indian geodetic data that were to consolidate his earlier findings and to lead to further important discoveries on the structure of the Himalaya, and the flexure of India.

He was awarded the Lyell Medal in 1908, elected a Fellow of the Royal Society in 1911, and served as President of the Geological Society of London 1920-1922. He was elected a Fellow of Imperial College in 1932. In 1908-1908, (and probably earlier, he lived in Shawford, Hampshire close to the Isle of Wight and his colleague, the seismologist, John Milne. In 1908, while at this address, Lawson and Gilbert sent him a copy of their 1906 San Francisco earthquake report. In 1917 he lived near Kew Gardens with his sister Dorothea in Broomfield Road, Richmond, Surrey. When she died he gave up the Kew house and in the early 1930's, in failing health took up residence in the spa town of Landrindod Wells, Wales, where he lived in the Gwalia Hotel opposite the entrance to the hot springs. He visited the south of France numerous times during this period and at the age of 74 wrote a sequence of articles on the evolution of the Rhone Delta since Roman and earlier times. He died 16 days before his 78th birthday on 15 July 1936 in the Gwalia hotel now an administrative office for the city of Landrindod Wells. Richard Oldham never married, but was survived by his youngest brother Henry Yule Oldham, a geographer at Cambridge University who himself died in 1951.

According to Sir Harold Jeffreys, Oldham claimed himself a geologist with little interest in seismology. It is not difficult to realize why he felt thus, since his 24 years marching through the mountains of deserts of India, often camping in relatively primitive surroundings, would have left an indelible imprint on his early life. Yet his contributions to seismology were seminal. He was the first to identify p- , s- and surface waves in early seismograms (Oldham,1899), and among the first to plot global travel-time graphs, the template for J-B travel time tables. Jeffreys characterized him as "the only man I ever met who did first rate work in a subject that disinterested him". His studies of earthquakes in India and the propagation of seismic waves led to his discovery of the core of the Earth (Oldham, 1906) and his investigation of travel paths through continents and oceans, hinted at the discipline of seismology now known as tomography. His analysis of gravity data from the Survey of India led him to infer the depth of sediments in the Ganges and the flexure of India (Oldham 1917) although this conclusion was dismissed by most geodesists at the time, and his findings have been forgotten by recent investigators. In 1898 during a clear-up of a Bombay branch of the GSI he discovered Baker's 1846 levelling survey across the Allah Bund, which had been lost by the publisher, but which subsequently led him at the age of 68 to publish a leasurely but insightful account of the 1819 M>7.9 Allah Bund earthquake near Bhuj (Oldham, 1926). He may well have been the first to coin the word "geophysics".

Among his first published articles are four that saw the completion (when he was 21-23) of unfinished manuscripts started by his late father (T. Oldham) whom he credits with 73 articles on the geology of India in his 1888 bibliography. Davison's obituary of R. D. Oldham indicates that he authored "more than 40 articles" on geology and seismology, citing from Holland's commentary on Oldham's retirement in 1902. Middlemiss in 1737 recognised more than 70, drawing on his readings of the indices of the Memoirs, and Records of the Geol. Surv of India. In fact he wrote than 90 articles and commentaries. I separate his publications roughly into his Rugby, Indian, Hampshire, and London periods, and they can be mostly downloaded as pdf's in these sections or in the chronological list of publications linked to these pages.