I’ll admit, when I get going, I can tell a tale but it is certainly never “off the cuff.” It takes hours of preparation. While I don’t follow my script exactly (I was never good at rote memorization), I often write a script for each talk I give before an audience. Attached is my script for this month’s 18th Century Science Day at Pottsgrove Manor. I hope to see you there.

18th Century Science Day Talking Points

While we all know the ramification of Enlightenment thinking on politics in the 18th Century, it also had a profound and seminal effect on science. Prior to the Enlightenment, scientific thought, when it could be separated from theology, was dominated by theories of absolute truth but over the course of the 16th and 17th Centuries this absolutism began to be replaced by modern empirical observation and experimentation. The world doesn’t work as it does because it should, or because of supernatural forces, but rather it follows series of natural laws. Rocks don’t fall to the earth because, as Plato argued, they belong to the earth; they fall because, as Newton observed, objects are attracted to each other in proportion to their mass and inverse proportion to their distance separation [squared]. God, if involved at all in the process at all, is the author of laws that govern the universe, not the prime mover who physically controls each particle. This subtle shift in focus drove an explosion of scientific inquiry and the creation of the “gentleman scientist.”

While we all know the ramification of Enlightenment thinking on politics in the 18th Century, it also had a profound and seminal effect on science. Prior to the Enlightenment, scientific thought, when it could be separated from theology, was dominated by theories of absolute truth but over the course of the 16th and 17th Centuries this absolutism began to be replaced by modern empirical observation and experimentation. The world doesn’t work as it does because it should, or because of supernatural forces, but rather it follows series of natural laws. Rocks don’t fall to the earth because, as Plato argued, they belong to the earth; they fall because, as Newton observed, objects are attracted to each other in proportion to their mass and inverse proportion to their distance separation [squared]. God, if involved at all in the process at all, is the author of laws that govern the universe, not the prime mover who physically controls each particle. This subtle shift in focus drove an explosion of scientific inquiry and the creation of the “gentleman scientist.”

A “Gentleman Scientist” corresponds widely with others who are exploiting this new “scientific method.”   We are willing to challenge the status quo on EVERYTHING from physics to politics.  We conduct a wide variety of scientific investigations, and we are focused on shifting our understanding of how the world works from folklore and tradition to mathematical scientific “laws.”  More importantly, however, like we are doing today, we share our learning through lectures, letters, and demonstrations.

So, as Gentleman Scientist, I have brought you some state of the art, 1773, breaking science, not for you to just hear about, but for you to experience with your own senses.  For you to try.  Come and observe for yourselves and draw your own conclusions. 

These are topics that we plan to discuss:

The Colonial Surveyor — A learned man of technology not theology

If you got a Bachelor’s Degree in the 1760’s it was likely not in science.  We only had a few colleges in America and they focused primarily on teaching Law and Theology (often together) as these were considered practical and useful education.  Gentleman scientists like Thomas Jefferson and Benjamin Franklin didn’t learn science and mathematics in school.  In fact, DOCTOR Franklin never attended college!  Science and math were learned through practical hands on education.

One avenue for acquiring both the means to pursue science and the necessary mathematical acumen was employment as a surveyor.  Surveyors using the very basic tools you can see in our presentation and the fundamentals of plane geometry, trigonometry, and astronomy explored and mapped our continent.  Men like George Washington went west and made the maps, laid out the roads, and parceled the land.  Often paid in the very land they surveyed, surveyors drove the western expansion after the Revolution and made it possible for new technologies like canals and turnpikes.  With the proceeds of selling the land they were given as part of their surveyor’s contract; these men acquired the wealth necessary to conduct later scientific inquiries.

Today, I have a hands-on exercise for those willing to try their hand at surveying.  We have a Gunter’s Chain (66 ft long), a plane table, some compasses, an alidade, paper and pens.  All the necessary gear of an 18th Century surveyor.  We are going to use these basic tools to measure and map a portion of the estate.

Celestial Observations – our 18th Century GPS

Surveyors and mariners know that certain heavenly bodies don’t appear to move, like the North Star.  They also used the fact that other, closer bodies (like the sun and the moon) move in predicable and stable patterns. So, using very simple instruments, and a bit of math, it is possible can tell exactly where we are on earth. 

I brought some of these instruments for you to experiment with.  Here’s a telescope much like the one used by Galileo who was punished for his observations of stellar parallax (more on this later) by the Roman Inquisition.  Here’s a sextant which looks complicated but is really just a big protractor for measuring angles.  Because Galileo was able to determine there is no stellar parallax – its true! – we can measure the angle between the horizon (north) and the North Star, and from that establish our Latitude.  You will also see a sundial.  With this simple instrument, I can determine local Zenith (about noon) and we can measure the angle of the sun to the horizon (west) and determine our approximate Longitude.  OF course, to be exact, I need a chronometer, like the one in my pocket, so I can determine the difference between the local noon and noon at the Royal Observatory in Greenwich.

1763 and 1769 Transit of Venus – “Big Science” in the 18th Century

Now, remember Galileo who made that heretical statement that the stars don’t revolve around the earth (none of them, not even the sun).  Much to the consternation of the Roman Church, only the moon circles the earth.  But we do know that 7 planets circle the sun (Neptune will not be discovered by William Hershel until 1781, and Percival Lowell’s Pluto will be a planet only from 1929 to 2000), and you can see all of them with this telescope.  Knowing the planets circled the sun allowed Johannes Kepler in 1619 to establish that the period of each planets orbit is proportional to its distance from the sun (actually  but proportional is close enough…).  The only thing we don’t know is the actual distances.

With planets circling the same point in space, it is only a matter of time before Mercury and Venus pass between the Sun and the Earth.  One of these passes is called a transit and Venus will transit twice in the 18th Century, in 1763 and again in 1769.  The reason why a Transit of Venus is so important takes us back to the fact that stars don’t show parallax but eclipses caused by the Moon and the planets do.  They look different from different locations on the earth (e.g. partial solar eclipses).  This lead Edmund Halley (yeah the comet guy) to propose that if we measure the time it takes Venus to cross the disk of the sun during its transit, we can, through the same trigonometry used by our surveyors, calculate the actual distance between the Earth and Venus and thus the distances between all the planets and the Sun.  The problem is that we must take multiple measurements from very distant locations on the Earth and this is something that can only be done in 1769 by the British Empire with its Royal Navy.

In 1769, an international team of observers went to eighteen locations across the globe – Canada, New England, New Spain, Cairo, all across the Russian Empire, India, and, most famous of all, Tahiti.  Here in Pennsylvania, our own David Rittenhouse set up an observatory near Dover and David West went to Providence.  Using their data, the American Philosophical Society in Philadelphia was able, in 1771, to estimate distance to the Sun as 24,000 times the radius of the Earth.  The Royal Society published their estimate, using all the data, in 1772 as 92.8 million miles – a 3% difference.  (This value will stand until 2004 when it is correct to 93.825 million miles).  So, in 1772, we now know the size of our Solar System!

But that’s not all we learned.  Remember, in the modern 18th Century, we share our learnings with our esteemed colleagues of the Royal Society, and also the Russians, Prussians, Spanish, and even the French (sigh).  So, here’s a letter by Vladimir Shiltsev of the Russian Imperial Academy of Sciences and he took observations in both ’61 and ’69. But he and Captain Cook also reported their errors.  Each party had two telescopes a few miles apart (2/92million ≈ NOTHING) and each team found showed SLIGHTLY different transit times for the two observation station.  Interestingly though, the differences between the two observers in Tahiti and those in St. Petersburg (9500 miles away) were the SAME and the match was too similar for it to be coincidence.

Mr. Shiltsev’s team had a better telescope and he was able to see a fuzzy outline.  From this, he claims that Venus, like Earth, has an ATMOSPHERE, and that could mean that there may be life beyond our world.  Let us hope and pray that the Roman Inquisition never enters the courts of Catherine.

Spontaneous Generation – Dispelling “myth and magic”

Before the Enlightenment, people believed that the world was literally managed, “hands on” by one or more gods (Jews, Christians, and Muslims believed in only one but we are not the only people in the world).  This leads to some really bizarre assumptions.  For example, if you never see flies hatch from eggs it is not unreasonable to assume that maggots simply “Spontaneously Generate” from decaying flesh.  After all, one day there are none, and a few days later they are everywhere.

Now we know how big animals reproduce.  People of the 18th Century were not stupid but with regard to microscopic organisms, which are poorly understood in 1700’s (Leeuwenhoek published his study of microbial life in 1673) the argument that “God made them appear” held some credibility.  Beer and wine spontaneously ferment.  Food spoils spontaneously.  Water becomes brackish for mysterious reasons and people get sicknesses from “Bad Air” (Malesia).  This is the idea of Spontaneous Generation.

Now one of the advantages of our time (1770) and being members of the British Empire, is that we have the ability to share written correspondence with fellow “Natural Philosophers” all over the world.  So, I would like to share a letter form the Right Reverend Needham that was recently published by the Royal Society.  As you can see, he builds on Leeuwenhoek’s initial observations using a microscope and argues that creatures, no matter how small, can only come from similar creatures.   Just like a horse can only come from the union of a mare and a stallion. 

From that experiment, I have devised my own.  Before you are two jars of sugar water, both boiled so that no life exists in them.  They are sealed but before they were sealed, I took the strobe, or spent yeast, from a local brewer and placed just a spec in the bottle.  As you can see, the bottle with the spec is fermenting but not the other.  BEER comes from some creature that makes BEER.  God may have made the creature but he did not put it in the beer.  Thus, the yeast must be present in the air, even though we cannot see them.

Electricity – Making science accessible to the masses even in the 18th Century

I’m going to conclude my talk with a nod to Pennsylvania’s famous Doctor Franklin and his experiments with “Electric Fire.”  I have a generator here very similar to what Dr Franklin uses in his workshop and I brought it here today because unlike the alchemist of old, we are not trying to discover secrets but rather uncover truths.  Science demands that the things we discover be discoverable by others so we try to repeat each other’s experiment. 

Thales of Myletes, an ancient Greek philosopher, experimented with “electric fire” using a cat’s fur and an amber rod.  His conclusion as that the “fire” must come from the animal.  We can rub amber and glass with fur and generate electricity so our experiments would tend to support Thales’ hypothesis but we have recently learned more.  In 1752, Benjamin Franklin captured “electric fire” from clouds, not an animal source at all.  Furthermore, just a few years earlier in 1745, Peiter van Musschenboek von Leiden found that electricity can be stored in a jar like this (show Leyden Jar).  Today we know that electricity will flow from a high concentration to a lower one and can be held for short periods these jars.  Furthermore, we all have the ability to experiment with it and it behaves the same way for everyone.  If only there was a practical use for this electricity, it might just change the world…

Published by Michael Carver

My goal is to bring history alive through interactive portrayal of ordinary American life in the late 18th Century (1750—1799) My persona are: Journeyman Brewer; Cordwainer (leather tradesman but not cobbler), Statesman and Orator; Chandler (candle and soap maker); Gentleman Scientist; and, Soldier in either the British Regular Army, the Centennial Army, or one of the various Militia. Let me help you experience history 1st hand!

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