Overview
Recherches de la cause de l’excentricité des couches ligneuses qu’on apperçoit quand on coupe horisontalement le tronc d’un arbre is a scientific memoir by Georges-Louis Leclerc, Comte de Buffon (1707–1788). Its subject, announced fully in its long descriptive title in the manner customary for eighteenth-century academic papers, is the observed fact that when the trunk of a tree is cut across horizontally, the concentric growth rings—the “woody layers”—are usually not truly centred on the pith. Instead their centre is displaced to one side, so that the layers are wider on one side of the trunk than the other. Buffon’s paper takes this eccentricity as a natural-historical problem and seeks to determine its cause.
The work belongs to the earlier, less famous phase of Buffon’s career, before he became known throughout Europe as the author of the monumental Histoire naturelle. In these years Buffon was active as a mathematician, an experimentalist, and a student of forestry and the physical properties of wood, and he was building the reputation within the Académie royale des sciences that would culminate in his appointment to direct the Jardin du Roi. This memoir is characteristic of that formative period: a focused empirical inquiry into a single, precisely defined phenomenon of plant growth, pursued in the analytic, cause-seeking spirit that Buffon shared with the physico-mathematical science of his day.
Author and intellectual context
Buffon was born in Montbard in Burgundy and trained first in law and then in mathematics and the physical sciences. In the 1730s he was drawn into the circle of the Académie des sciences in Paris, where his early contributions ranged across geometry and the calculus of probabilities—he is remembered in mathematics for the problem now called “Buffon’s needle”—and across natural philosophy. He translated important British scientific works into French, including Isaac Newton’s treatment of the method of fluxions and Stephen Hales’s Vegetable Staticks, the latter a foundational study of the mechanics and physiology of plants. Hales’s experimental approach to the movement of sap and the growth of vegetables left a clear mark on Buffon’s own interest in trees.
A substantial part of Buffon’s activity in this period concerned forestry and the science of timber. As a landowner in Burgundy with woodlands of his own, and as a man closely concerned with the practical needs of the French state, Buffon undertook extended experimental studies of the growth, cultivation, and strength of trees and wood. This research had an eminently useful dimension: the strength and durability of timber were of direct importance for construction and above all for naval shipbuilding, a strategic preoccupation of the French monarchy. Buffon carried out systematic trials on the mechanical resistance of wood and produced memoirs on the conservation and improvement of forests and on the qualities of timber. The present study of the eccentricity of the growth rings sits within this broad program of inquiry into the structure and physiology of trees, standing at the intersection of botany, physics, and the applied concerns of the forester and the timber merchant, who had every practical reason to understand how the wood of a trunk is laid down and why it varies around its circumference.
Subject and approach
The phenomenon the memoir addresses is one long familiar to woodsmen and to anyone who has examined a cut stump: the annual layers by which a tree grows in thickness are commonly not deposited evenly all around the trunk. When the trunk is sectioned horizontally, the pith—the geometric starting point of the tree’s growth—is frequently found off-centre, the rings being crowded on one side and more widely spaced on the other, so that the “centre” of the concentric figure is displaced. Buffon’s title frames this as a recherche de la cause: an investigation into why this unequal, eccentric growth occurs rather than the even, truly concentric growth one might naively expect.
The memoir treats the question as a natural problem to be resolved by observation and reasoning about the conditions under which trees grow, rather than as a matter of mere description. In doing so it exemplifies the method Buffon applied to his forestry studies generally: careful attention to the physical circumstances of a tree’s development and to the way growth in thickness proceeds through the successive deposition of woody layers. The topic connects directly to the questions Buffon pursued elsewhere about how trees grow, how their wood is formed, and what governs its strength and quality, so that an apparently narrow curiosity about the geometry of a cross-section opens onto larger issues of plant physiology and the structure of timber.
Place in Buffon’s work and significance
Within Buffon’s body of work this memoir belongs to the cluster of technical papers on trees, wood, and forestry that he produced before and alongside the launch of the Histoire naturelle, whose first volumes appeared in 1749. These forestry and timber studies are less celebrated than the great natural history that made Buffon one of the most widely read authors of the eighteenth century, but they were an important part of his scientific formation and of his standing in the Académie des sciences. They show him as a practising experimentalist and observer of the living world, engaged with concrete problems of plant growth and of the material properties of wood, and they anticipate the sustained attention to trees, vegetation, and the economy of nature that runs through his later writings.
The study of ring eccentricity also reflects a durable strand in the history of botany and forestry: the effort to read the record of a tree’s life from the pattern of its growth rings, and to relate the form of the wood to the conditions—of exposure, situation, and environment—under which the tree grew. As a contribution by one of the leading naturalists of the Enlightenment to that inquiry, the memoir is of interest both for its specific subject and as evidence of the kind of patient, cause-seeking natural science that Buffon practised in the years when he was establishing himself, and that he would later carry, on a far grander scale, into the Histoire naturelle.
