Continuing allure of the lodestone

Driving Force

十一月 8, 1996

In a world where even bankers seem to believe that young men in New York or Singapore can use the philosopher's stone to transmute paper into gold, it is not surprising that an author, hoping to introduce the general public to the significance and use of magnetism, should include the word "magic" in his title. Like tenth-century scientists in Byzantium addressing an equally credulous and superstitious public, he must, in Gibbon's words, amuse their curiosity without oppressing their indolence.

This is a book full of facts about magnets and magnetic materials, their composition, their history and their uses and at its end the general reader, if none the wiser, will certainly be better informed. Even engineers and scientists familiar with magnets may pick up a few useful titbits of information. Since it makes no use of mathematics, except to explain scientific notation (109, etc), the book should not oppress anyone's indolence and, although the author says that he wrote it for adults, it could equally be used to amuse the curiosity of children.

The author is an enthusiast of, and also a convincing spokesman for, materials science, and so the book is at its best when it deals with the materials of magnetism, their composition (ferrites, steels and neodymium iron), their classification as soft (for transformers) or hard (for permanent magnets) and with how their properties depend on their microstructure. It is good, too, on the history of magnetism and its traditional applications as well as those more modern applications which, in the last half-century, have resulted from the discovery of materials with much better properties.

There is a worthwhile discussion of how the niobium alloys, discovered at Bell Telephone Laboratories in the 1950s, have made powerful superconducting magnets possible, and some sensible words about the hype accorded to the latest, ceramic, "high-temperature" superconductors. Far less publicity greeted either the appearance of the revolutionary, and very cheap, ferrite magnets in the 1950s or the much more powerful rare-earth materials in the 1980s, though both of these have had a major impact on technology and economics (the operation of a television set depends on about a kilogramme of ferrite magnets).

Because the Chinese named the lodestone a "loving stone" and the French call a magnet un aimant, the first two chapters adopt a whimsical style, excessive enough to put many readers off before they get to the core of the book. This is a pity for, all told, it is a suitable introduction for a layman to an important aspect of modern technology, and the extensive list of further reading at the end may tempt a few readers whose curiosity has been more amused than their indolence has been oppressed.

F. N. H. Robinson, emeritus fellow, St Catherine's College, Oxford, has written on electricity and magnetism for the Encyclopedia Britannica.

Driving Force: The Natural Magic of Magnets

Author - James D. Livingston
ISBN - 0 674 21644 X
Publisher - Harvard University Press
Price - £15.95
Pages - 311



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