On the day following the guillotining of Antoine Laurent Lavoisier, mathematician Joseph Louis Lagrange lamented the loss of the man commonly considered the father of modern chemistry. "It took them only an instant to cut off that head," he said, "but it is unlikely that a hundred years will suffice to reproduce a similar one."Although he lived only to the age of 51, Lavoisier revolutionized the field of chemistry. He created the first modern table of chemical elements, recognized the role oxygen plays in the rusting of metals, demonstrated that water-previously considered one of the four fundamental elements-is a compound of hydrogen and oxygen, and asserted that the total weights of the products of a chemical reaction must equal the total weights of the reactants.Yet despite his remarkable importance to modern chemistry, Lavoisier's scientific work was more a hobby than a profession. In fact, because he made his living as a tax collector, his scientific work was relegated to early morning and after-dinner hours. Appropriately, the picture Poirier paints of Lavoisier is that of the whole man-not only a scientist but a successful financier, respected economist, and influential administrator as well.