Driftig veen en onderaards bos

Nicolaas Witsen, het landschap van Amstelland en de grondbeginselen van de moderne geologie

Samenvatting

Nicolaas Witsen (1641-1717) was not just a prominent administrator and diplomat, but also something of a polymath. He delved into geography, cartography, navigation and shipbuilding, as well as ethnography, philology, history, botany, zoology and astronomy. Apart from scientific curiosity, his choice of subjects was influenced by the interests of Amsterdam, of which he was lord mayor on several occasions: thus he took an interest in the expansion of trade, ship building technology and hydraulic engineering works.

This article discusses a manuscript by Witsen that we date to the second half of the 1650s: Natuer van de gront rontsom Amsterdam, door mij in de jeugt opgestelt (Nature of the ground around Amsterdam, penned by me in my youth). The manuscript consists of a series of detailed notes of his own observations, supplemented by ideas and observations at second hand. We discuss the themes Witsen touches on in a set order: firstly Witsen’s observations, then his own interpretation, and finally the modern interpretation of what Witsen observed.

Witsen described the soil structure in and around Amsterdam, both outside and inside the dikes, probably based on drilling data. He described the stratigraphy systematically, from bottom to top. He then tried to explain the variations in the soil structure, using not just his own observations, but also data from deeper drillings, such as the famous one carried out by Pieter Ente in 1605, which reached a depth of 73 metres. From this he deduced how the soil must have come into being under the influence of the sea. Witsen encountered large numbers of bog oaks – a subterranean forest – which he believed to have contributed to peat formation. He also described the discovery of a tree-trunk canoe, which he compared with the boats used by the Indians in New Netherland.

Witsen’s manuscript attests to keen powers of observation and a rigorous scientific method. He combines philology with empiricism, while giving considerably more weight to the latter. Witsen describes how, over the course of time, sand and clay were deposited and peat was formed and how those layers were influenced by one another and by human intervention. His manuscript reflects a view of the world as a dynamic system, an idea that underlies modern geology, which tries to deduce the age of layers of earth using stratigraphy. The basic principles of stratigraphy, laid out in 1669 in the celebrated Prodromus by Witsen’s friend Nicolaus Steno, can be found in Witsen’s manuscript, making it the first written record of the thinking behind the Steno Laws, which must have emerged from an exchange of ideas between the two men.

It is hardly surprising that these insights were gained in Amsterdam. For one thing, Amsterdam was evolving into a centre of scientific endeavour in the seventeenth century, for another, it was located in the West Netherlands peat region where the dynamics of landscape development were clearly visible in the soil. Urban expansions and hydraulic engineering and construction projects entailed interventions in the soil, leading to the inadvertent creation of ‘peepholes’ for studying the soil structure. Knowledge of the soil structure and landscape development was far greater in the seventeenth century than we realize. Thanks to the rise of an internationally oriented and scientifically aware urban elite, that practical know-how became part of a much broader flow of knowledge: the scientific revolution of the seventeenth century.