WHAT WONDERS the English traveler in the 16th and 17th century reported: the southern skies over St. Helena, an earthquake in Tokyo, swarms of flies invading ships in the Marshall Islands and Italians using forks.

The focus of the Folger Library's current exhibit, the English travelers made literary milestones. They were monarchs and merchants, ambassadors and explorers, pilgrims and students. In this display that includes about 80 rare old books, Francis Bacon's essay on travel advises the young student-traveler to keep a diary, visit churches, monuments, monasteries, antiquities, ruins, warehouses and gardens. His advice in 1625, still good, was to "sucke the Experience of many."

They did keep journals, and some, such as Richard Stonley, teller of the Exchequer, were faithful to them. The diaries of William Dampier, the third Englishman to circumnavigate the globe, inspired Defoe and Swift.

Travel stimulated ideas. Edmund Halley sailed to the south Atlantic to catalogue the stars. And in 1638, Francis Godwin told how to fly to the moon, using swan power.

One original author drew up a table of distances between towns. Another, in 1595, composed a book of useful phrases in seven languages (English, Italian, German, Flemish, French, Spanish and Latin). The phrases also prescribed proper behavior when stopping at an inn, warned about highwaymen and, as signposts didn't exist, gave this advice on finding directions: Ask a shepherd.

Thomas Coryate's travelogues from the early 1600s displayed such unbridled enthusiasm that Ben Jonson said of him: "Seeing the word Frankford, or Venice, though but in the title of a Booke, he is readie to breake doublet, crack elbowes, and overflowe the roome with his murmure."

By contrast, Bishop Joseph Hall believed that experience sufficient for most could be had from books. If God had wanted the British to travel, He wouldn't have built a moat around them. And Hall observed a common error: "an humorous giddiness to measure the goodness of anything by distance of miles." THE ENGLISH TRAVELLER -- At the Folger Shakespeare Library through mid-April, 1985.