ALL THE STEAM in the world, Henry Adams wrote early in the 20th century, could not have built Chartres -- only the Virgin. In emphatic testimony to Adams' words, the National Cathedral, like some gothic airship of stone and glass, hovers above Washington, construction at a standstill, its west front honeycombed with scaffolding. In a country of such awesome power and wealth, it is ironic that the National Cathedral remains unfinished.

What force other than "steam" is needed to raise a cathedral today? The Last Cathedral , by Ty Harrington, a former writer/photographer for National Geographic magazine, is a sensitive but indirect response to that question. Obviously, money and power are prerequisites; otherwise, construction would still in progress. Certainly the very best materials and the most proficient artists and artisans are also necessary. But perhaps even more significant are men of vision and dreams -- a breed of men fast dwindling -- who are willing to give their lives to a work greater than they.

Harrington by no means intends to criticize American values. Very simply, his purpose is to relate, through lucid text and eloquent photographs, the story of the National Cathedral. But in plainly and gently telling that story, Harrington cannot avoid underlining the nation's own lack of vision and imagination.

Harrington's approach is effective because it is uncluttered and straightforward. He devotes a single chapter to every aspect of the cathedral: its stone, stained glass, sculpture, iron work, tapestry, music and bells. Like a stained-glass window or embossed capital, the book intrigues by its assemblage of facts and detail. Who first drew the plans for the cathedral? How have they been changed? What are the duties of a mason? How is a stone laid? What happens when an error is committed? How were the great bells cast?

One is overwhelmed by the intricacies that building a cathedral involves. The expertise necessary to center, plumb and level precisely even a single stone amazes: "A single stone out of line means the equilibrium is disturbed and the entire structure is liable to collapse. And, as though to lend a final twist . . . it is the nature of Gothic arches that they must be constructed from the top downward, not, in the usual fashion, from the ground up!" So soundly fashioned is the cathedral that the United States Bureau of Standards estimates "it will stand for over two thousand years without reinforcement or any major repairs." Most buildings today are constructed to last for 25 years.

But a cathedral is only as magnificent as the men who conceive and create it. Those associated with the National Cathedral have been men of singular genius and dedication, men, who in modern times, are anachronisms, throwbacks to medieval society.

Philip Hubert Frohman, the cathedral's greatest architect (who died in 1972), dedicated his life to a single vision: the completion of the cathedral, "glorified and perfected." An intense perfectionist, he deemed "hours spent on blueprints to change the radius of an arch by an inch" as nothing, provided "such a change would improve the building."

Dean of the Cathedral and chairman of the building committee, from 1951 to 1977, Francis Sayre was also ruled by that same purity of intention. "We are building an instrument that can be far more eloquent and permanent than all the sermons in the world," he often said. Asked about the steels rods embedded in the center of columns to absorb the shock of a sudden lateral thrust, Dean Sayre replied: "We realize there has never been an earthquake in this area . . . but if you're building for five thousand years, as we are, you never know what may happen."

Discussing the significance of the National Cathedral, Constantine Seferlis, sculptor and carver, speaks for all artists and builders: "The Cathedral is the most important work I have done; what we build here is a real contribution to our times because it goes back to an era when there was a true concern for craftsmanship. What a man does with his life is important, and at the Cathedral we give ours to history."

For the present, hammers and chisels are silent; construction has ceased. The work that remains, whenever it is resumed, will be stupendous. The two west towers alone, Harrington reports, will have over 4000 crockets -- "enough carving to keep a single craftsman busy for thirty years." Retired Master Carver Roger Morigi best captures the urgent plight of the unfinished cathedral: "In the world of today, patience is gone and there is no more desire to build things that last. Times have changed and cathedrals are too hard work. The young craftsman are too few, the costs are too high. There will never be another building like this -- this is the last cathedral."

Escalating costs, vanishing skills, a shortage of patience -- dire-sounding words these are. Yet Morigi at least assumes that the Cathedral will one day be completed, a monument in this city of monuments, dedicated not to mammon but to God.