The geological observations of Robert Hooke.

Ammonite fossil illustrations drawn by Robert Hooke (‘Discourse on Earthquakes’ from 1703).

Ammonite fossil illustrations drawn by Robert Hooke (‘Discourse on Earthquakes’ from 1703).

At the beginning of the sixteenth century and throughout the seventeenth century a great debate about the true nature of fossils started in Italy and extended to Europe. There was two hypothesis in dispute: the first one postulated an inorganic origin for the fossils (directly formed within rocks) and the second, which contemplated an organic origin. The court doctor to the Grand Duke of Tuscany, Nicola Steno argued that the stones called Glossopetrae or “tongue stones” looked like shark teeth because they were shark teeth deposited a long time ago. In 1667, Henry Oldenburg, the secretary of the Royal Society included an abstract of ‘The head of a shark dissected’ (Canis Carchariae Dissectum Caput) by Nicolas Steno in one of the early issues of the Philosophical Transactions. Robert Hooke (1635-1703), Curator of Experiments of the Royal Society, expressed similar ideas two years before Steno. In ‘Micrographia’ (1665) he  argued that the micro-structure of petrified wood were identical to those seen in normal wood. He also described the ‘serpentine stones’ and concluded that these stones were not formed due any ‘plastic virtue’, but were due to shells of shellfish that became filled with mud or clay or petrifying water and had over time rotted away, leaving their impressions ‘both on the containing and contained substances’ (Kusukawa, 2013).

Between 1667 and 1700, Hooke delivered a series of at least 27 lectures or ‘Discourses’ to the Royal Society on the generic subject of ‘Earthquakes’, or earth-forming processes, published in his Posthumous works (1705), and accompanied by some of Hooke’s drawings that survived among the papers of Sir Hans Sloane.

Hooke's drawing of fossil bivalves, brachiopods, belemnites, shark teeth and possibly a reptilian tooth (Copyright © The Royal Society)

Hooke’s drawing of fossil bivalves, brachiopods, belemnites, shark teeth and possibly a reptilian tooth (Copyright © The Royal Society)

Hooke’s ‘wandering poles’ theory was the first dynamic explanation of continent formation in the history of science. ‘The Earth’s rotation, he proposed, caused a bulge and thus greater altitude at the equator versus a flattening at the poles. He maintained that over time, a change in the positions of the poles on the Earth surface due to a change in the moment of inertia would cause different areas of bulging and flattening with the creation of new land or sea areas’ (Drake, 2007).

By the time that he delivered his third series of ‘Discourses’ in 1687, Hooke had arrived to three remarkable conclusions. First, that fossils were the petrified remains of once living creatures (he called ‘medals of Nature’ and part of ‘Nature’s Grammar’, to be collected like coins and read like texts) and not just twists in the rock. Second, that there had been radical changes of sea level. Third, that hill-tops in England had once formed the beds of tropical oceans as indicated by the discovered of gigantic sea shells.

Hooke’s writings were intimately connected to his birthplace: the town of Freshwater near the western edge of the Isle of Wight. Throughout his Discourses he mentioned the cliffs around Freshwater Bay from which he collected fossils. Unfortunately, many of the fossils that he collected for the Royal Society, along with his portrait as Secretary of the Society, many papers and several scientific instruments and models designed by Hooke are lost, but Hooke’s ideas were transmitted by later writers, demonstrating the continuity of the development of geological thought. Arthur Percival Rossiter even nominated him in 1935 as ‘The First English Geologist’.

Reference:

E. T. Drake, The geological observations of Robert Hooke (1635-1703) on the Isle of Wight; p19-30. Geological Society, London, Special Publications 2007, v.287; doi: 10.1144/SP287.3

Sachiko Kusukawa, Drawings of fossils by Robert Hooke and Richard Waller, Notes Rec. R. Soc. 2013 67 123-138; DOI: 10.1098/rsnr.2013.0013. Published 3 April 2013

M. J. S. Rudwick, The meaning of fossils: episodes in the history of palaeontology(University of Chicago Press, 1985)

 

The Salagrama stones and the early history of ammonite studies.

Ammonites  found near Yeovil in Somerset. From Natural History Museum database. © The Natural History Museum, London

Ammonites found near Yeovil in Somerset. From Natural History Museum database. © The Natural History Museum, London

Ammonites are the common name given to the subclass Ammonoidea, an extinct order of cephalopod. The first occurrence of ammonites is from the Devonian around 400 million years ago. The last surviving lineages disappeared, along with the dinosaurs, 65 million years ago in the Cretaceous–Paleogene extinction event.

Since antiquity, ammonites has been associated with myths, legends, religion and even necromancy. They were known as “Cormu Ammonis”, “Corni de Ammone” or “Cornamone” because their shapes resemble the tightly coiled rams horns used to represent the Egyptian god Ammon. Pliny the Elder (AD 23 – August 25, AD 79) referred them in his monumental work Naturalis Historia. He wrote: “The Hammonis cornu is among the holiest gems of Ethiopia, it is golden in colour and shows the shape of a rams horn; one assures that it causes fortune-telling dreams”. This could be explained because pyritised ammonites have a sparkling, golden appearance.

The salagramas are ammonites worshipped as divine symbols of Vishnu—the four-armed God, Sustainer of the Universe who holds a disc or wheel (chakra) in one of his hands.  In China, were described as horn stones ( jiao-shih) and they being used as an ancient remedy. Japanese referred them as chrysanthemum stones (kiku-ishi) and Buddhists interpreted them as a symbol of enlightenment.

Jeletzkytes spedeni, a fossil ammonite from USA. From Wikimedia Commons.

Jeletzkytes spedeni, a fossil ammonite from USA. From Wikimedia Commons.

They have been interpreted as petrified venomous snake (“ophites”) often called “serpentstones”. In medieval England, they were considered evidence for the actions of saints such Saint Patrick or St. Hilda of Whitby. According to tradition, these fossil Ammonites were  serpents that infested the region of Whitby,  before the coming of St. Hilda. This is cited in Sir Walter Scott’s Marmion:

“… Of thousand snakes, each one

Was changed into a coil of stone,

When holy Hilda prayed;

Themselves, within their holy bound,

Their stony folds had often found.”

Ammonite fossil illustrations drawn by Robert Hooke (‘Discourse on Earthquakes’ from 1703).

Ammonite fossil illustrations drawn by Robert Hooke (‘Discourse on Earthquakes’ from 1703).

Georgius Agricola, often named as “the father of mineralogy” and author of De Re Metallica, a work based on Pliny’s work Historia Naturalis, also referred them as Ammonis Cornu.  Conrad Gessner include some ammonite’s illustration is his work De rerum fossilium (1565). But even toward the end of 17th century the ammonite organic nature was still under debate. Robert Hooke was fascinated by the logarithmic coil of ammonite shells and their regularly arranged septa. He reached the conclusion that ammonites are not only of organic origin but also widely resemble Nautilus. A landmark in ammonite research was the classification scheme given by Johann Jacob Scheuchzer in 1716.

The modern form of the word ammonite was coined by the French zoologist Jean Guillaume Bruguière (c.1750-1798) in 1790, but only in 1884 the subclass Ammonoidea was formalized in zoological taxonomy.

References:

Marco Romano, From petrified snakes, through giant ‘foraminifers’, to extinct cephalopods: the early history of ammonite studies in the Italian peninsula, Historical Biology 2014, http://dx.doi.org/10.1080/08912963.2013.879866

Van der Geer AAE, Dermitzakis MD, De Vos J. Fossil Folklore from India: The Siwalik Hills and the Mahâbhârata, Folkore 119: 71-92. London: The Folklore Society (2008)