On the occasion of its centennial in 1887, William E. Gladstone paid the U.S. Constitution a handsome, if syntactically clumsy, compliment. It was, wrote the grand old man of British politics, "the most remarkable work known to me in modern times to have been produced by the human intellect, at a single stroke (so to speak) in its application to political affairs."

It would be national lese-majesty to doubt it, and few Americans do. But since Gladstone's is now the conventional judgment, it's a bit startling to renew acquaintance with the obstacles that the Philadelphia 55 faced that steamy summer nearly 200 years ago.

A betting man might have wagered that any of several difficulties would defeat their best efforts. There was the task of finding a representation formula (proportional representation, as demanded by the more populous states, or one-state-one-vote, as demanded by the small fry?); or ending the slave trade; or settling the future of the western lands. And that was only the surface.

What plainly saved the convention from these potential divisions was a stark reality. Failure to harness the centrifugal forces tearing at the new national fabric would expose the infant confederacy to sure dissolution. Imperial predators prowled its frontiers. Britain obstinately clung to its Great Lakes forts, in defiance of the Treaty of Paris. Spain controlled the Florida territory and had closed the Mississippi to U.S. trade.

The authors of "Decision in Philadelphia" assume, with no feeling they need prove, that the flimsy nation of the mid-1780s was in deep trouble. It had no executive worth the name, no judiciary and no way of collecting taxes from recalcitrant states.

The Colliers, Connecticut brothers, are able historians and clear writers. At crucial stages, they argue, it was the inventiveness and vision of the delegates that made the big difference. Everyone knows about James Madison's contribution. But they call to the stage for a belated bow such figures as James Wilson of Pennsylvania, Roger Sherman of Connecticut and Charles Cotesworth Pinckney of South Carolina.

The surpassing problem of 1787 (as every schoolboy knew when schoolboys knew their history) was the representation formula. In the Continental Congress under the Articles, every state cast one vote; all were equal. Madison was bent on introducing proportional representation, the "sine qua non," as he saw it, of a strong and effective union. This was the essence of his "Virginia plan." The small states were leery of it. Virginia and Pennsylvania might fear having their wealth soaked to bail out the deadbeats of Rhode Island and Massachusetts. The smaller states, except in the South, feared domination by the large. Delaware had even instructed its delegates to walk out if equal representation were lost.

No convention-splitting issue rivaled this one. The Colliers devote about a quarter of their book to a blow-by-blow account of how the convention groped its way to the solution we know today: the Senate, representing states equally; plus the House, representing population, with the decennial census thrown in to keep apportionment honest.

It is, as the Colliers note, an interesting irony that this consuming mutual distrust was to prove a false alarm. No important national division on big state-small state lines has ever occurred. In fact, it is about the only line of potential division that has played no important role at all in our post-1787 history.

"Decision in Philadelphia" treats each major problem separately. It is a defensible strategy, but it risks obscuring the subtle interconnections between various issues. It has the strange effect, in the end, of making the constitutional design seem more improvisatory than it really was. But that is a minor flaw.

I would be alarmed, however, if a new generation of constitutional buffs absorbed some of the Colliers' horseback attitudes. There is, for instance, the electoral college, which they call a "Rube Goldberg" device. They concede that this ingenious idea of James Wilson's was the key to the strong executive as the convention developed it. They unfortunately buy, in its most simple-minded form, the underexamined prejudice that the electoral college is a continuing menace to democracy, not an ingenious strong point of federalism.

That small burst of punditry aside, the Colliers have written a useful and readable introduction to that "most remarkable work" whose 200th anniversary we are poised to celebrate.