Ireland's early saints and heroes; The Flowering of Ireland: Saints Scholars and Kings, by Katharine Scherman. Boston: Little, Brown & Co. $16.95.

They were a colorful lot, the mythic ancient Irish. Comgall could spit hard enough to break a rock. Brigid hung her wet cloak on a sunbeam. Brendan made a sea journey that took him to what he thought was the mouth of hell, possibly iceland's volcano, Hekla.

Despite images like these, some have viewed early Ireland as a cultural and religious backwater whose exquisite works, such as the "Book of Kells," are just anomalies in an otherwise primitive history. by bringing us closer to many characters from Irish history, Katharine Scherman's book does much to lay these claims to rest.

Designed for a general audience, her volume covers prehistoric and pagan Ireland, the major individuals who led the conversion to Christianity, art and architecture, and the challenges faced by the people between the 5th and 12th centuries.

Ms. Scherman not only deals with the Irish at home, but she also tells how they brought Christianity to the Continent during the Dark Ages. She visited many, if not all, of the places about which she has written, and her vivid, firsthand accounts make her readers feel they are right beside her.

Some early monks, Scherman explains, braved the most inhospitable conditions imaginable to seek a higher spirituality through self-purification.

Those on the small island of Skellig Michael, for instance, were cut off from the mainland much of the year. Living on what was little more than a huge rock in the North Atlantic, they sheltered in beehive-shaped huts, ate wild birds, fish, and scurvy grass, and raised a few goats.

The early Christians who went abroad also faced deprivations, perhaps more than they expected. When St. Columba settled near the Swiss-German border of france, conditions were so primitive that he and his companions lived for days on herbs and tree bark.

"Once," Scherman recounts, "during a specially lean period, one of the brothers fell ill.The others, having nothing to eat anyway, decided to call their privation a purposeful fast, and to spend their hungry days and nights praying for him. After three days they were all near death; then 'suddenly they saw a man standing before their gates with . . . a supply of bread and condiments.'" He told them an impulse had moved him to share these goods and asked the monks to pray for his sick wife. The woman recovered, and their living conditions improved, the author tells us.

Deciding whom to include and how much to tell about each individual isn't an easy task for any historian, especially not with subjects as lively as these irascible Irish saints. And a book that attempts to cover much may gloss over certain points about which there is scholarly debate. For instance, one simply can't go into the politics that led to the creation of the story of St. Patrick's driving the serpents out of Ireland many centuries after the alleged event took place.

Nor can one explain all the details of the rivalry between Irish and Roman missionaries which culminated at the Council of Whitby in 664. Scherman spells out the basic elements with considerable clariy, however. Theological points -- the cut of the tonsure and the methods for dating Easter -- were ostensibly the matters the king was asked to arbitrate. But a lot more was at stake: Would Britain join the bulk of Christendom on the Continent? Or would it choose the isolation of Celtic Christianity? The king was a practical man, and his decision to go with Rome changed the course of Celtic history.

Nicely illustrated with black and white photographs, this book is a fine introduction to early Irish history.