Fifty millennia ago, through Greek and Roman times and on to the dawn of the 19th century, flame remained man's sole illuminant. Lightning, until then reserved to the gods, was electrical; but as electricity in its controllable manifestations became more familiar, both the electric spark and the hot glowing wire attracted the attention of inventors, from Sir Humphry Davy (1778-1829) in 1808, who demonstrated both these electrical sources using batteries invented by Alessandro Volta (1745-18).
Carbon electrodes, brought so close together that a spark passes, can be drawn apart to lengthen the spark and produce more light. Practical difficulties meant a half-century delay in passing from Davy's demonstrations to practical inventions. The spark was the first to be harnessed; by 1863 two light houses were employing arc lamps.
Next to become usable, and to meet the need for low-intensity domestic lighting, was the incandescent wire. In this case the slowness of development was mainly due to the search for a suitable filament. Repeated heating and cooling is apt to break a filament, air must be excluded by a glass bulb to avoid oxidation, and a very good vacuum pump is needed. Where the wire enters and leaves the bulb expansion and contraction present difficulties, since metal and glass expand differently. These problems were all solved; electrical discharge lamps requiring no filament soon followed.
Brian Bowers, a senior curator at the Science Museum, Kensington, London, is an historian of technology and biographer. Lengthening the Day is a charming book, illuminated with photographs of objects and places of historical interest. Clearly none of the several electrical inventions he describes sprang, as from the head of Zeus, in a single flash; many people participated, some of them also known for their scientific work as distinct from the art of practical invention.
Paul Israel's book is a detailed and extensively referenced account of Thomas Edison's 84 years. It progresses smoothly and readably, conveying not only the details of technical matters and the surrounding circumstances but also much of human interest about this extraordinary human subject. Two chapters on Edison's childhood clearly reveal the multi-faceted mind that would soon lead to his well-known inventions.
Edison's technical innovations were both numerous and diverse; he also invented or was associated with the development of such crucial foundations of modern life as the light bulb, street lighting including the necessary dynamos and rights of way, facsimile, motion pictures, music recording, and the microphone. Israel relates how these modern miracles came about and enlivens the stories in the telling. He is editing the multi-volume edition of Edison's papers.
Why is it that university courses on chemistry and physics rarely mention Edison or, if they do, make clear, sometimes in a condescending way, that he was no scientist? What is the difference between scientist and inventor, or between engineer and inventor for that matter? Watt is always known as an engineer. J. G. Crowther interpreted Edison's downgrading as class snobbery, parallelling Plato's dismissal of manual activity as inferior to philosophy, a legacy that remains with us today, despite the sublime manual works of the Greeks that include harbours and docks, warships, mines, tunnels, canals, sculpture and the Parthenon. Undervaluing the admirable contribution of Edison to society is surely just another symptom of scientific illiteracy.
Ronald N. Bracewell is emeritus professor of electrical engineering, Stanford University, California, United States.
Lengthening the Day: A History of Lighting Technology
Author - Brian Bowers
ISBN - 0 19 856548 8
Publisher - Oxford University Press
Price - £24.99
Pages - 221