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Encyclopedia Britannica

HOPKINSON, JOHN (1849-1898)

This article appears in Volume V13, Page 686 of the Encyclopedia Britannica.

Encyclopedia Britannica - Main :: HIG-HOR

HOPKINSON, JOHN (1849-1898) , English engineer and physicist, was born in Manchester on the 27th of July 1849. Before he was sixteen he attended lectures at

Owens

OWENS, JOHN (1790-1846)

College, xnd at eighteen he gained a mathematical scholarship at Trinity College,

Cambridge

, where he graduated in 1871 as senior wrangler and first

Smith

's prizeman, having previously taken the degree of D.Sc. at London University and won a

Whitworth

WHITWORTH
WHITWORTH, SIR JOSEPH

scholar-ship. Although elected a fellow and tutor of his college, he stayed up at

Cambridge

only for a very short time, preferring to learn

practical

PRACTICAL

engineering as a pupil in the works in which his father was a partner. But there his stay was equally short, for in 1872 he undertook the duties of engineering manager in the glass manufactories of Messrs Chance Brothers and Company at Birmingham. Six years later he removed to London, and while continuing to act as scientific adviser to Messrs Chance, established a most successful practice as a consulting engineer. His

work

WORK

was mainly, though not exclusively, electrical, and
his services were in

great

GREAT

demand as an expert witness in patent
cases. In 18no he was appointed director of the Siemens labora-
tory at King's College, London, with the title of professor of
electrical engineering. His death occurred prematurely on the
27th of August 1898, when he was killed, together with one son
and two daughters, by an accident the nature of which was
never precisely ascertained, while climbing the Petite Dentde Veisivi, above Evolena. Dr Hopkinson presented a rare combination of

practical

PRACTICAL

with theoretical ability, and his achievements in pure scientific research are not less intrinsically notable than the skill with which he applied their results to the solution of concrete engineering problems. His

original

ORIGINAL

work

WORK

is contained in more than sixty papers, all written with a complete mastery both of style and of subject-matter. His name is best known in connexion with electricity and magnetism. On the one hand he worked out the general theory of the magnetic circuit in the dynamo (in conjunction with his brother Edward), and the theory of alternating currents, and conducted a long

series

SERIES (a Latin word from serere, to join)

of observations on the phenomena attending magnetization in iron, nickel and the curious

alloys

ALLOYS (through the Fr. aloyer, from Lat. alligare, to combine)

of the two which can exist both in a magnetic and non-magnetic state at the same temperature. On the other hand, by the application of the principles he thus elucidated he furthered to an immense extent the employment of electricity for the purposes of daily life. As regards the generation of electric energy, by pointing out defects of design in the dynamo as it existed about 1878, and showing how important improvements were to be effected in its construction, he was largely instrumental in converting it from a clumsy and wasteful appliance into one of the most efficient known to the engineer. Again, as regards the distribution of the current, he took a leading part in the development of the three-wire system and the closed-circuit transformer, while electric traction had to thank him for the

series

SERIES (a Latin word from serere, to join)

-parallel method of working motors. During his residence in Birmingham, Messrs Chance being makers of glass for use in lighthouse lamps, his attention was naturally turned to problems of lighthouse illumination, and he was able to devise improvements in both the catoptric and dioptric methods for concentrating and directing the beam. He was a strong advocate of the group-flashing system as a means of differentiating lights, and in-vented an arrangement for carrying it into effect optically, his plan being first adopted for the catoptric light of the Royal Sovereign lightship, in the English Channel off Beachy Head. Moreover, his association with glass manufacture led him to study the refractive indices of different kinds of glass ; he further undertook abstruse researches on electrostatic capacity, the phenomena of the residual charge, and other problems arising out of Clerk Maxwell's electro-magnetic theory.
His

original

ORIGINAL

papers were collected and published, with a memoir by his son, in 1901. -

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