WASHINGTON. — The dust of America's 12th president has been disturbed in a Louisville, Ky., tomb. A coroner and a forensic anthropologist are seeking to still or confirm speculation that Zachary Taylor, not Lincoln, was the first president assassinated. Whatever is learned in this investigation will serve human happiness by underscoring the lovely contingency of history.
If Taylor was deliberately poisoned, the foul deed most likely was done by Southerners angry about his opposition to the expansion of slavery. If so, the plotters fell victim to the vagaries of things. They may have saved the Union by making more likely the failure of the South's eventual resort to arms.
Taylor's condition in his final days was consistent with arsenic poisoning. If that occurred, traces of arsenic will be detectable in bits of hair, fingernails, bones and other tissues.
What happened on Thursday, July 4, 1850? What usually happens on the Fourth of July, only more so. There was much speechifying. The country did not yet have major-league baseball or MTV to entertain it. Rhetoric was popular entertainment. And that day, in 1850, the president was on hand at a ceremony at the unfinished Washington Monument.
It was a typical high-summer day in 19th-century Washington -- sunny, hot, humid and dangerous. Humidity is natural to this river town, and was even worse then, before the draining of the marsh that lay, breeding mosquitoes, where the Tidal Basin and Jefferson Memorial now are.
The danger arose from the nature of mid-19th-century urban life, the abundance of horses and animals in the midst of human population, the absence of sanitation measures and of scientific understanding that soon would produce public health advances concerning housing and food handling.
Orators did rattle on in those days, so Taylor broiled in the sun for several hours, refreshing himself with ice water, chilled buttermilk and cherries and perhaps other fruits and vegetables. Washingtonians had been told to avoid such things because the country was experiencing epidemics of Asiatic cholera.
That night Taylor was uncomfortable. The next day he worked a bit, but by Saturday his family was alarmed. An Army surgeon diagnosed ''cholera morbus,'' an elastic 19th-century term denoting a variety of intestinal ailments. He died on July 9.
''Old Rough and Ready,'' as his troops affectionately called him, was the hero of the battle of Buena Vista in 1847. He was a Southerner who owned 140 slaves, but he was a strong-willed military nationalist who said he would personally take the field and hang secessionists.
Furthermore, he opposed the expansion of slavery. He said that if Congress passed the Wilmot Proviso, banning slavery in territories acquired from Mexico, he would sign it. The Congress never passed it. If Taylor had lived, might it have?
When he died he was on the verge of sending to the Congress a message demanding immediate admission of California and New Mexico as free states and settlement of a New Mexico-Texas border dispute in favor of the former.
Now, it is conceivable that had he lived, he might have cowed secessionists into permanent peaceableness. But it is much more likely he would have provoked secessionists, bringing on bloodshed.
Daniel Webster said at the time: ''If General Taylor had lived, we should have had a civil war.'' We would have had it before another decade of growth of the North's strength through industrialism and immigration, and before the birth of a new political party that found a nation-saving leader in a former Illinois congressman who had opposed the war that had made Taylor a hero and hence president.
History is a rich weave of many threads. Many of them, if pulled out, could cause a radical unraveling, setting the past in motion as a foaming sea of exhilarating contingencies.
For more than a century we have been plied and belabored by various historicisms purporting to prove that what happened had to happen, that history is a dry story of the ineluctable working of vast, impersonal forces unfolding according to iron laws of social evolution. People, the historicists say, are mere corks bobbing on powerful currents. This demoralizing doctrine denies the possibility, ultimately, of meaningful self-government, for individuals or nations.
That is why either way the Louisville investigation turns out -- blame unsanitary cherries or blame unscrupulous opponents -- Taylor's death tantalizes. It gives a glimpse of an always inspiriting prospect -- possibilities, paths not taken. Things could have been different; choices and chance cannot be scrubbed from the human story; we are not corks; we matter.
The fate of a president 141 July Fourths ago whispers in our ear: ''The river of history could have cut a different canyon.''
George F. Will is a syndicated columnist.