--
"Trust me. I have a lot of experience at this."
General Custer's unremembered message to his men,
just before leading them into the Little Big Horn Valley
__________________________________________________________
<The Sea Shell on the Mountain Top>
-Alan Cutler
The author is a writer affiliated with the Smithsonian Institution. He
received his Ph.D. for work in geology.
We physics teachers frequently structure elementary physics courses as
a battle. A battle between the Aristotelian biases with which our incoming
students are equipped and the great enlightenments which came to us through the
revolutionary conceptions of Galileo and, subsequently, Newton.. After reading
this book , however, I realized that the Galilean-Newtonian revolution might be
thought of as pretty "small potatoes" compared with the impact upon our culture
of the insights of Nicolaus Steno. Steno was a skilled anatomist,, darling of
European royalty, priest, contemporary of Galileo - and the inventor of the
science of geology.
The book opens with Steno in Florence doing a public dissection of the
head of a Great White Shark. The time is about a generation after Galileo's
confrontation with the church. We learn that Steno is a skilled anatomist,
supported by the influential Medici family, and that the shark dissection
triggered thoughts in his mind about an often-debated question of the time -
why are seashells often found far from the sea, sometimes embedded in solid
rock at the tops of mountains?
The ancient Greeks had a simple explanation, namely, that the seas
occasionally overflowed the land. Later European thought, we are told,
included the speculation that the fossils grew in the rocks. Christian dogma
taught that the earh was only 6,000 years old, leaving little alternative to
the idea that the fossils were found where they grew.
What is the connection of all this with the shark dissection? Cutler
returns to the dissection in Chapter 5. Steno, whose methodically kept notes
have been published,, knew that the resemblance between the shark's teeth and
certain stones - known as tongue stones- had been commented on a century
earlier. Tongue stones were found on barren surfaces after heavy rainstorms
and were prized for magical and medicinal purposes; the Island of Malta
exported large quantities. Guillame Rondelet, a Montpellier physician and
naturalist, had made the daring suggestion that tongue stones were, in fact,
petrified shark's teeth.
Steno was born in Copenhagen during the 30-years war. His father died
in early life, but his mother kept the family supported trough a succession of
marriages. Steno enrolled as a medical student at age 18 at the University of
Copenhagen. where he kept a journal, ``Chaos'', that still survives.
Steno's supervising professor was Thomas Bartholin, famous for the
discovery of lymph vessels in the human body. Bartolin was well known as a
crowd pleaser when he gave popular lectures and demonstrations of cadaver
dissection.
Barttholin retired from teaching shortly after Steno entered the
university,, but the two apparently formed a bond. Bartholin traveled
extensively, largely in Italy - with at least one trip to the island of Malta,
and diligently collected sea shells and other fossils from the mountains. He
even wrote a book on the magical curative powers of his findings. He had
previously written a book on the curative powers of unicorn horns (subsequently
revealed to be narwhal tusks - with, apparently, no loss of magical
properties). Steno was intrigued. He wrote in his journal:
Snails , shells, oysters, fish, etc., found petrified in places far
remote from the sea. Either they have remained there after an ancient
flood or because the bed of the sea has slowly been changed.
The last nine words were underlined..
Steno escaped (the thirty-years war was in progress) from Copenhagen
without graduating from the university, and wandered across northern Europe,
giving lecture demonstrations of his dissection skills and writing scholarly
papers on subjects related to medicine. Having become famous as an anatomist,
Steno packed his bags and headed for Florence where disciples of Galileo had
formed an academy devoted to experimental sciences.
In Florence, Steno found favor with the Medici family, which gave him
support. He was able to consider questions like, what mechanism could be
responsible for depositing fossils, such as seashells in layers of earth? He
reasoned from his own observations in laboratories at the university, that the
shells must have been carried by water, with the earth then solidifying about
them. That is, the fossils were deposited as part of sedimentary layers.
Steno published his arguments, cautiously worded, in 1667 as part of an article
describing his dissection of the shark's head.
Although he was now turning his attention to geologic matters, he made
at this time one of his most important anatomical discoveries. He discovered
that females of live-bearing species produced eggs.
He also converted to Catholicism, a step that could put his life in
danger if he returned to his native Denmark.
Continuing his researches, he wrote, as apparently, almost no European
ever had before, ``In various places I have seen that the earth is composed of
layers superimposed on each other at an angle to the horizon.'' An exception
was Leonardo da Vinci, whose notebooks described the sedimentary strata of
Tuscany, which Steno was observing, in great detail. Another notable exception
existed in the Islamic world.
Then the great realization came to Steno when he cracked open a pearl
and saw how a sequence of layers had been built upon a grain of sand.
Sequencing was the clue. The sedimentary layers of the earth functioned as a
clock - the lowest ones were earliest in time. In other words, the history of
the earth and the creatures who lived on the earth could be recovered by
looking a layers that were far below the surface, Such layers could be seen in
mines and the sides of mountains. And the age of a deposit could be determined
by counting layers.
Steno wrote a summary, promising a complete dissertation on his new
discovery, ````Prodromus to a Dissertation on Solids Naturally Enclosed in
Solids''.
He set out, in his summary, principles and techniques for analyzing the
substances and objects that could be recovered from the strata of earth. In his
brief summary, which still exists, including an english translation (the
original was in latin), That summary created geological science.
There is more. Steno became a bishop and turned to religious matters,
but his work took on a life of its own. That life was aided by the dawning
industrial revolution which began to emphasize the economic value of minerals,
whereby Steno's geology found practical application.
My main criticism of this book is that it meanders. The meandering is
often enjoyable with lots of human interest asides, but for me, the science
sometimes got lost in the diversions. As any, who have followed this far can
tell, this is a hard book to summarize. But I recommend it highly, as an
introduction to the life of one of the most ingenious scientists of all times.
And, as the author notes, there is not yet a definitive biography of Steno.
--
"Trust me. I have a lot of experience at this."
General Custer's unremembered message to his men,
just before leading them into the Little Big Horn Valley