A History of Research and a Review of Recent Developments

Introduction xix
Bertram Hopkinson was an outstanding researcher. His father, John
Hopkinson, was a consulting engineer and inventor who had applied his scientific
skill to the development of the quality of optical glass, and to its use for lighthouse
illumination. Bertram was born in 1874, was a day boy at St Paul’s School, and
had won a major scholarship to Cambridge before he was 17. He read for the
Mathematical Tripos. When he left university at the age of 22 he entered the
legal profession and was called to the Bar in 1897. He was on his way to Australia
to carry out a legal inquiry when he received news of his father’s death in a
climbing accident in Switzerland. Bertram was recalled to London, and
immediately decided to give up his legal career in order to complete his father’s
unfinished engineering work. With his uncle, Charles Hopkinson, and assisted
by Mr Talbot, he was subsequently responsible for the design of electric tramways
at Crewe, Newcastle and Leeds. The partners wrote a paper on Electric Tramways
for the Institution of Civil Engineers in 1902, and were awarded the Watt Gold
Medal. In 1903, at the age of 29, Hopkinson was elected to the chair of Mechanism
and Applied Mechanics at Cambridge. For the next ten years, under his leadership,
the Engineering School increased in numbers and repute.
He served as joint Secretary of the British Association Committee on Gaseous
Explosions, whose reports contain records of many of his experiments. At the
outbreak of the First World War he dropped all other interests and obtained a
commission in the Royal Engineers. He concerned himself with the collection
of intelligence, and in conducting experiments in connection with an arrangement
for the protection of warships from the effects of mines and torpedoes, the hull
‘blister’. The blister was able to absorb the energy of an explosion by becoming
deformed. Just before the war he had written papers on the measurement of
pressure due to the detonation of high explosives or by the impact of bullets (the
famous ‘Hopkinson Bar’ experiments), and on the effects of the detonation of
gun cotton. He thus became the foremost expert in Britain on the protection of
ships and structures against explosions, and also on the design of attack weapons,
such as aircraft bombs. From this he became interested in the armament of
military aircraft generally, and worked at a secret experimental station at
Orfordness. By June 1918 he had become Deputy Controller of the Technical
Department of the Air Force. He learned to be a pilot and generally flew alone.
On 26 August 1918, he crashed near London in bad weather and was killed.
Bertram Hopkinson was aloof from any consideration of private advantage
or personal convenience. Nothing ruffled his serenity or impaired his judgement.
His death at the age of 44 was a tragedy and the science of flame and explosion
suffered a great loss. This summary of his life and work has been taken from
a Royal Society memoir. His scientific papers were collected and arranged by
Ewing and Larmor in 1921 and published by the Cambridge University Press.
I have dwelt at length on the history of Hopkinson for two reasons. The
first is to underline that Hopkinson, because he was not trained within the
high walls of a narrow engineering field, was free to apply his creative thought
across the whole area of Applied Mechanics, Physics and Electrical Engineering.