Niccolò Stenone, as the Italians call him, was born in Copenhagen in 1638; his real name was Niels Steensen, later latinized to Nicolaus Steno. As a youth he devoted himself with success to the study of anatomy. His subsequent journeys to visit universities and scholars in various European cities took him to Italy where he remained for some years as guest of the brother of the Grand Duke of Tuscany (which explains his burial in the basilica of San Lorenzo in Florence). Here he lived in immediate contact with the fertile cultural environment of Pisa and Florence, where the experimental sciences flourished no less than letters, and was able to dedicate himself to study and research in the field of Geology in subject matter ranging from fossils and minerals to the structure of the Tuscany Apennines.
But that period in Stenone’s life was marked by a profound change in his religious spirit, including his conversion from the Lutheran to Roman Catholic faith. Following a brief return to his homeland he made his way back to Florence where in 1675 he entered the priesthood.
From then on he fervently dedicated himself to apostolic missionary work in the north of Europe until his death in 1686 in Schwerin, in present-day Germany. The Grand Duke of Tuscany obtained the removal of the body to Florence where it rests in the Medici crypt in San Lorenzo. In 1988 Stenone received recognition as a “servus Dei” and was beatified.
In his brief years in Tuscany Stenone, with his lively, acute intelligence and his propensity to reason on the basis of direct observation of data, had taken new and promising paths toward the understanding of natural phenomena in a field where the few brilliant intuitions were nullified by beliefs based on myth, superstition and dogmatism. His famous Prodromus (De Solido intra Solidum Naturaliter Contento Dissertationis Prodromus, On a Solid Contained Naturally within Another Solid. Introduction to a Dissertation), written in 1669 before his return to his homeland, remains a testimony to science; in it are to be found cues and ideas resting on concrete reasoning, and which would enter into the common heritage only a century later. Among such are to be recalled the intuition regarding the constancy of crystallographic forms in minerals, something which would come to be formulated as a strict law by French mineralogist Romé de l’Isle only in 1772; as well as his intuition in the field of stratigraphy concerning the principle of original horizontality and the principle of superposition.
But the modernity of Stenone’s thought is even more evident when he speaks “of the different changes that have taken place in Tuscany”. His numerous careful observations made in many localities led him to affirm that “the present state of a given object reveals the past state of that same object”, meaning that the study of how rocks appear today can reveal the past geological history of the area. As an example, Stenone reconstructed the history of Tuscany using an area that might be the Valdarno, a midsection of the Arno river valley, or similar low-lying area surrounded by Apennine mountains, and he did so using ultramodern geological cross sections. The geological structure of the Valdarno can be schematized as follows: two parallel elevations formed by ancient sedimentary rocks of marine origin, well stratified, separated by a sector sunken along faults and partially filled in by other, more recent sedimentary rocks (sands and clays) deposited at a former lake site; at present the Arno runs through the low-lying sector, where its sediment deposits are accumulating (see figure).
But let us listen to the words of Stenone, describing his own geological cross sections: “The six figures, while illustrating how we can deduce six aspects of Tuscany different from its present state, at the same time serve to comprehend more easily what we have said regarding the Earth’s strata. The dotted lines represent the sandstone strata so defined on the basis of their principal element, even though mixed in with them are found differing strata both clayey and hard; the remaining lines represent rocky strata likewise so-defined on the basis of the principal element present, even though situated between these are, at times, other strata softer in substance. Figure 25. presents a cross section of Tuscany during the era when the rocky strata were still intact and parallel to the horizon. Figure 24. illustrates notable cavities dug out by water and fire, without any deterioration of above strata. Figure 23. shows mountains and valleys arisen from the collapse of upper strata. Figure 22. represents new strata created by the sea in said valleys. Figure 21. depicts the eroded part of lower strata, without any deterioration of above strata.
Finally, Figure 20. presents hills and valleys produced there by the collapse of sandstone upper strata.”
Above and beyond the “technical details”, which have been superseded by later findings (the “empty spaces” that precede the collapses evidently correspond to blocks sunk due to tectonic movements), what remains intact is the intuition that “the change in natural things is certainly incessant”, expressed at a time when it was commonly held that the Earth was originally formed just as it is today. Stenone states, “We recognize six distinct aspects in Tuscany, since it was twice fluid, twice flat and dry, twice uneven (meaning broken up by collapses)”.
But Stenone’s revolutionary ideas did not bear the fruit they deserved, certainly due at least in part to his early retirement from the scientific scene, but perhaps as well to a certain hostility on the part of many of the leading scientists toward a recent convert to the Roman Catholic faith at a time when the important science centres were located in the predominantly Protestant great cities of central and northern Europe.
Just as in the case of Leonardo da Vinci, Stenone may be considered a founder of modern geology, for he was an enlightened forerunner who clearly hit upon the right road leading to a better understanding of our planet.