meteorology. In one experiment, Nicolas-Théodore confirmed Boyle's law by a new method: He carefully weighed a tightly closed flask at many different altitudes and found that the differences in weight were exactly proportional to the differences in barometric pressure readings. In other research in the physical sciences, he named the mineral dolomite after Déodat Gratet de Dolomieu, in March 1792. Nicolas-Théodore was attracted to chemistry by Lavoisier's discoveries, and he adopted Lavoisier's new system of chemistry early in life. He became interested in the chemistry and physiology of plants, including gas exchange and the ways that different soils affected their growth. His early papers on these subjects laid the groundwork for some of the chapters in his magnum opus, Recherches chimiques sur la Végétation ("Chemical Research on Plant Growth"), published in 1804. This book was the first summation of the fundamental process of photosynthesis and a major contribution to the understanding of plant physiology. In contrast to some of his predecessors in the field of photosynthesis research, Saussure based his conclusions on extensive quantitative data that he had collected. In Recherches chimiques sur la Végétation (1804) Saussure showed that the increase in the mass of a plant as it grows could not be due only to the uptake of CO2, but was also a result of the incorporation of water into plant dry matter. He demonstrated this by showing that plants grown with their roots in water and their shoots in an atmosphere of ordinary air with added CO2 increased in dry weight by an amount much greater than could be attributed to the assimilation of the CO2 gas available to them. Plainly, the weight increase had come from the water. In addition, Saussure demonstrated that plants obtain their carbon from the carbon dioxide in the atmosphere, not through uptake from humus in the soil, as his immediate predecessors in photosynthesis research had generally believed. He also showed that plants require mineral nutrients, which they take up from the soil, and nitrogen, although he did not trace the source of plant nitrogen definitively to the soil. Saussure's finding that the source of plant minerals was the soil disproved the widely held view that mineral substances in plants arose from vague "transmutations" within the plant. His work enabled completion of the basic, overall chemical equation of photosynthesis, according to which carbon dioxide and water, in the presence of light, are converted