LAST LETTERS Prisons and Prisoners of the French Revolution, 1793-1794 By Olivier Blanc Translated from the French by Alan Sheridan Michael di Capua/Farrar, Straus and Giroux 250 pp. $22.50

BY THE STANDARDS of the 20th century, the attempted decimation of the French aristocracy by Dame Guillotine during the infamous Year II of the French Revolution appears, in retrospect, to have been pretty tame stuff, hardly more than an incomplete and amateurish attempt at mass destruction by men unschooled in the arts of applied fanaticism. In terms of sheer volume, the agonies of the inmates of the Conciergerie, the brooding building on the banks of the Seine that housed the Revolutionary Tribunal, offer the lightest of hors d'oeuvres when compared with the ante rooms of Dachau or Stalin's gulags. Indeed, in the hectic two months of June-July 1794 which preceded Robespierre's fall, a mere 1,370 people climbed the scaffold. Even by suppressing evidence, refusing to allow defense lawyers, or not troubling to interrogate the accused, the best the Tribunal could manage was 54 death sentences in a single day -- that of 28 Prairial.

Of course, tragedy, unlike genocide, is best measured by the thimbleful. That is why this collection of letters dashed off by those whose call before the Tribunal was tantamount to a death sentence retain a special poignancy. The poignancy is intensified when one realizes that these last claims of innocence, protestations of love and regret dispatched with trembling hand to wives, children and husbands, requests to settle debts and, above all, pleas not to be forgotten, never reached their destinations but were intercepted and until now interred in the common grave of the public prosecutor's files in Paris' Archives nationales.

What Last Letters evokes so brilliantly is the picture of a society fixed in a twilight between life and death. So eager was the Terror to round up its opponents, that it was forced to convert former convents, hospitals, schools, barracks and even palaces into prisons to house the waves of inmates brought in on the merest suspicion of disloyalty. Here the enemies of the Republic awaited their call before the Tribunal -- the nobles held their salons and "kept up the strictest etiquette," ex-generals of the Revolution whose lost battles earned for them a chance to explain themselves to the Tribunal discussed tactics, fallen politicians debated, "the rich look after the poor with good grace. Everybody fraternizes."

Yet, outside the maisons de sante', four-star establishments where the wealthiest inmates were allowed to purchase a degree of freedom and even luxury, prison life was not without its trials. At the barracks of the Carmes on the Rue de Vaugirard, the prisoners were ". . . not properly dressed, wear nightshirts and dirty pantaloons, their legs bare, a handkerchief around their heads, their hair uncombed, their beards unshaven." Women would sometimes bribe their way in to see a lover, often in a desperate attempt to get pregnant thereby securing a stay of execution. Others, like the crapulous Pepin-Desgrouettes, a legless cripple and former Jacobin incarcerated for corruption, attempted to survive by implicating his fellow inmates in imaginary escape attempts. On 6 Thermidor, only three days before Robespierre's fall ended the Terror, he gave evidence before the Tribunal that sent 74 prisoners to their deaths, including a 16-year-old boy executed because he threw a herring "filled with worms" at the head of his jailer. Despite its desperate grasp for normalcy, prison life was carried out in the shadow of the scaffold -- the prisoners held mock trials and even simulated executions, which served to prepare some so well for their ordeal that as one of the players climbed into the tumbrel, he could announce that, "Today's the actual performance: you'll be surprised how well I know my role."

The moment of ultimate dread occurred when an officer of the court appeared with the list of those whose time of trial had come. The prisoners were assembled in the hall and the names read out. Those called had just enough time to say their last farewells, give away their possessions to those who remained, some of the women to change into their best clothes scrupulously preserved for this ultimate occasion, or scratch out a last, hasty letter which too often never reached its intended destination.

The scene at the Conciergerie was a vision of despair. Some already condemned lay on filthy mattresses staring into space. "Women and their husbands, mistresses and their lovers sat on rows of benches placed against the walls. Some caressed one another with as much carefree gaiety as if they were in rose arbours. Others looked very sad and were shedding tears . . ." But it was here amidst the swarm of abusive guards, many of whom were drunk, and crowds of idlers, spectators and prostitutes who made the corridors outside the courtroom "like a backstreet," that courage was most often apparent. The most celebrated example was offered by a common prostitute named Catherine Halbourg whom a scheming politician of the Terror had hoped to have executed with Marie-Antoinette as a last insult to the Bourbons. As she passed the Duc de Chatelet who, half-drunk, was blubbering in terror, she said: "You must learn, Monsieur le Duc, that those who do not have a name acquire one here, and those who have one must learn how to bear it."

The trip from the Conciergerie to the guillotine on the Place de la Revolution could take up to an hour. The route was sometimes lined with those who came to look for famous faces, and who seemed enraged if the condemned were calm or laughed, covering them with abuse or even throwing mud. At the place of execution, some asked for a glass of brandy, others a chamberpot. Jean-Jacques Barbot, a schoolmaster, shouted "Long live the King!" "and, as his hands were being tied, the indignant onlookers poured abuse upon him and demanded with loud cries that they be shown his head." Madame de Kolly, wife of a rich merchant accused of sending money out of the country, "let out a long, frightful cry before the blade struck her." Many, however, like cavalry Captain Armand Custine, walked up the steps and placed their heads in the "window" with a calmness which must have belied their inner turmoil: "Why, then, should I feel any unease?" he had written. "To die is as necessary and as simple as being born." Police noted that, after the sixth execution, the crowd began to drift away.

DESPITE THIS indelible picture of the expiation of the "enemies" of the Terror, Last Letters is in many ways a curious book, half historical treatise and half raw archive. The very fact that Olivier Blanc deals with letters that were intercepted probably because the public prosecutor, the odious Fouquier-Tinville, wished to gather financial or political intelligence seems to have skewed his historical perspective. The author interprets the revolution as a tissue of plots, lies and financial conspiracies of which the chief victim, in his eyes, was not so much the authors of his letters as Robespierre himself.

But what of the many others, simple men without wealth or political connections who were also dispatched to their deaths by the Tribunal: priests who refused to swear an oath of allegiance to the Republic because the pope forbade it, and especially peasants accused of hoarding because they declined to sell their produce at fixed government rates paid in worthless assignats? Why are not their letters preserved in the archives? Blanc does not ask himself this question. Nor does it seem to occur to him that this eloquent silence might suggest explanations for the Terror that go beyond the rather facile conspiracy theories he lays out. While the desire to keep capital at home was certainly a legitimate goal for a government desperate to finance its wars, the Terror was more than a strategy to counter the economic warfare of the aristocracy. Robespierre required the combination of internal conspiracy and external threat to keep his increasingly repressive regime afloat. He was addicted to the guillotine, and like those whose last days Blanc so vividly chronicles, was also destined to be its victim.

Douglas Porch, Mark W. Clark Professor of History at The Citadel, is the author of "The Conquest of Morocco" and "The Conquest of the Sahara."