CORRECTION (PUBLISHED 24 MARCH 1994) INCORPORATED INTO THIS ARTICLE

JOHN STOYE's books describe people and parts of Europe that are left out of everyone else's. English Travellers Abroad: 1604-1667, published more than 40 years ago and recently reissued with considerable revisions by Yale University Press, opened a window through which little had previously been visible. A subsequent volume on the later 17th century in the Fontana History of Europe, and a masterpiece, The Siege of Vienna (by the Turks in 1683), extended this revelation of what lay off the autoroutes of European history.

In these excursions he is equipped, in addition to a thorough general knowledge of the period, with an unobtrusive expertise in military history and geography. In this last he has the advantage of hindsight: in the 17th century accurate maps of the Continent were still hard to come by, and the men and armies he writes about had to do their best without them. In this connection the hero of his latest book, Luigi Fernando Marsigli, though hitherto unknown, is shown to be a figure of some importance.

Marsigli was born in 1658, into the urban aristocracy of Bologna, the meaningless ceremonial emptiness of which had reduced the life of one of Europe's most intellectually stimulating cities to deepest torpor. The young Marsigli, after one brief spell of ceremonial nonsense, escaped to a diplomatic mission in Istanbul, sent out by the Republic of Venice. After that he never looked back. A born traveller, he was curious about everything, particularly about natural phenomena, and, to a lesser degree, about archaeological remains. If he reminds us of John Aubrey, he altogether lacked Aubrey's passion for gossip and interest in character.

While in Istanbul, or on his way there, he gathered a great deal of information about the civil and military organisation of the Ottoman Empire and copied some classical inscriptions. He also made a scientific study of the currents in the Bosphorus, the salinity of the water and the fish that swam there. In addition to the primitive apparatus at his disposal for these observations, he made close inquiries among the local fishermen. Hydrography and geography were to be the fields of knowledge to which he was to make his greatest contribution.

Back in Italy, he cast round for further foreign employment. His scientific bent, his knowledge of mathematics and his readiness to sketch and draw maps opened possibilities as a military engineer. In 1683, when the Turks were assembling their forces for the great thrust at Vienna, the Emperor needed officers. Marsigli was enrolled in a regiment then on the Danube frontier. After the briefest period of square-bashing, he was employed to examine defence works and then detached to survey territory through which the Ottoman offensive was to be expected.

Its onrush took the world, and him, by surprise. Captured by the Tartars, whose lightning mobility would have been impossible for a regular force, he was lucky, by pretending to civilian status, to stay alive. He made coffee for the Turkish forces besieging Vienna, until, sold from one master to another, he was ransomed and returned to Italy. Undeterred, he at once reentered the emperor's service and spent the next 15 years in the Balkans, mapping unknown and sparsely inhabited country, advising on fortification and commanding a regiment. During this period he was, deservedly, elected a fellow of the Royal Society, and was the first man to plot the course of the Danube below Buda with any accuracy.

The War of the Spanish Succession saw Marsigli, now a general, transferred to the western front. Here, as second in command of the great but inadequately manned and stored fortress of Breisach, he was involved in its surrender in 1703. The next year, after a court martial, his chief was shot and he was dismissed with ignominy, to devote the remaining 26 years of his life to learned correspondence, the publication of his scientific and geographical papers, and the endowment of his native city with the fruit of his collections.