THOMAS NEWCOMEN (1663-1729)

1712 – England

‘Uses the property of condensing steam to create a partial vacuüm in a cylinder and therefore pull a piston. The system was highly inefficient but was used to pump water from mines’

Today, the credit for the steam engine is usually given to James Watt, while the name Thomas Newcomen remains shrouded in obscurity.

The design of his low-pressure steam engine involved heating water underneath a large piston that was encased in a cylinder.

Steam that was released as a result of the heating forced the piston upwards. A jet of water was then released from a tank above the piston. The sudden cooling of the steam made it condense, creating a partial vacuüm which atmospheric pressure then pushed down on, forcing the piston downwards again. The piston was attached to a two-headed lever, the other side of which was attached to a pump in the mineshaft. As it moved up and down, the lever moved likewise and a pumping motion was created in the shaft, which could be used to eject floodwater.

The first engine could remove about 120 gallons per minute, completing about twelve strokes in that time, and had the equivalent of about 5.5 horsepower. Even though the engine was still not particularly powerful, was hugely inefficient to run, and burnt huge amounts of coal, it would work reliably 24-hours a day.

The steam engine originally developed by Newcomen for work in the mines was quickly developed by engineers like JAMES WATT and RICHARD TREVITHICK (1771-1833) into the steam locomotive.

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DANIEL FAHRENHEIT (1686-1736)

1715 – Netherlands

‘The kelvin scale is more suitable for scientific purposes and the celsius scale is neater, based on decimals. The advantage of using the fahrenheit scale is that it is designed with everyday use in mind, rarely needing negative degrees’

Even as late as the start of the eighteenth century, scientists had no reliable means of accurately measuring temperature and a uniform scale by which to describe the limited measurements they could make.

Fahrenheit thermometer

FAHRENHEIT THERMOMETER

GALILEO had used the knowledge that air expands when heated and contracts when cooled to build a primitive instrument. Using a cylindrical tube placed in water, he noted that when the air in the device was hotter, it pushed the level of the water downwards, just as it rose when the air-cooled. He realised that readings from the device were unreliable because the volume and therefore the behaviour of the air also fluctuated according to atmospheric pressure. Gradually scientists began using more stable substances to improve the accuracy of the reading, with alcohol being introduced as a possible substitute late in the seventeenth century.

Fahrenheit knew that the boiling points of different liquids varied according to fluctuations in atmospheric pressure; the lower the pressure, the lower the boiling point. A producer of meteorological instruments, he first achieved progress in 1709 with an improved alcohol thermometer. Building on the work of GUILLAUME AMONTONS (1663-1705) who investigated the properties of mercury, Fahrenheit took the measurement of temperature into another domain. He produced his first mercury thermometer, particularly useful in its application over a wide range of temperatures, in 1714.

In 1715 he complemented his breakthroughs in instrument making with the development of the fahrenheit temperature scale. Taking 0degrees to be the lowest temperature he could produce (from a blend of ice and salt), he used the freezing point of water and the temperature of the human body as his other key markers in its formulation.

In his initial calculations, he placed water’s freezing point at 30degrees F and the body’s temperature at 90degrees F. Later revisions changed this to 32degrees for the freezing point of water and 96degrees for the body temperature of humans. The boiling point of water worked out to be 212degrees F, giving a hundred and eighty incremental steps between freezing and boiling.

picture of the head and face of DANIEL FAHRENHEIT ©

DANIEL FAHRENHEIT

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PIETER VAN MUSSCHENBROEK (1692-1761) EWALD JURGEN VON KIELEL (1700- 48)

1745 – Holland/Germany

‘Electricity produced by electrostatic machines can be stored in a jar’

The Leyden Jar

diagram of the use of the 'LEYDEN JAR'

In modern terms the Leyden jar is a capacitor or condenser.
In 1734 Stephen Gray (c.1666-1736), an English experimenter, discovered that electric charge could be conducted over distance. He also classified various substances into conductors and insulators of electricity. He suggested that metals were the best conductors and thus introduced the use of electric wire.

In 1734 Musschenbroek, a professor from Leyden in Holland discovered that electricity could be stored in a jar of water.
During the same year, von Kleist, a German scientist also discovered the same principle independently.
In later versions of what became known as the Leyden jar, water was replaced by copper foil inside and outside the jar.
The Leyden jar became a novelty and in village faires magicians used ‘electricity in a bottle’ to amaze and entertain villagers.

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CAROLUS LINNAEUS (1707- 78)

1735 – Sweden

‘A system for naming organisms by assigning them scientific names consisting of two parts’

Portrait of Linnaeus ©

LINNAEUS

Each species is given a two-word Latin name – The genus name that comes first and begins with a capital letter, and the species name, which begins with a lower case letter. The genus name is often abbreviated, and the names are always written in italics or underlined. The Linnaean system has six classification categories – in descending order, kingdoms, phyla, classes, orders, genera and species. Only two are used for naming organisms.

German botanist Rudolph Camerarius (1665-1721) had shown that no seed would grow without first being pollinated. In 1729, Linnaeus wrote in a paper about ‘the betrothal of plants, in which … the perfect analogy with animals is concluded’. He insisted that it is the stamens where pollen is made (the ‘bridegrooms’) and the pistils where seeds are made (‘the brides’) that are the sexual organs, and not the petals as had been considered previously.

As botanists and zoologists looked at nature, or ‘Creation’, there was no way of classifying the animal kingdom depicted in bestiaries of the time but alphabetically; or of distinguishing the real from the mythical.

Linnaeus developed a system of classification. Starting with the plant kingdom, Linnaeus grouped plants according to their sexual organs – the parts of the plant involved in reproduction. Each plant species was given a two-part Latin name. The first part always refers to the name of the group it belongs to, and the second part is the species name.

Linnaeus divided all flowering plants into twenty-three classes according to the length and number of their stamens – the male organs – then subdivided these into orders according to the number of pistils – female organs – they possessed. A twenty-fourth class, the Cryptogamia, included the mosses and other non-flowering plants.

illustration of flower reproductive structures ©

Many people were offended by the sexual overtones in Linnaeus’s scheme. One class he named Diandria, meaning ‘two husbands in one marriage’, while he said ‘the calyx might be regarded as the labia majora; one could regard the corolla as the labia minora’. For almost a century, botany was not seen as a decent thing for young ladies to be interested in.

Linnaeus’s scheme was simple and practical and in 1745 he published an encyclopedia of Swedish plants, when he began considering the names of species. Realizing he had to get the names in place before someone else gave plants other names, he gave a binomial label to every known plant species and in 1753 published all 5,900 in his Species Plantarium.

Believing his work on the plant kingdom complete, he turned his attention to the animal kingdom. In his earlier Systema Naturae of 1735, he had used the classification ‘Quadrupeds’ (four-legged creatures) but replaced this with Mammals, using the presence of mammary glands for suckling young as a more crucial distinguishing characteristic. The first or prime group in the Mammals was the primates, which included Homo sapiens (wise man). His catalogue of animals was included in the tenth edition of Systema Naturae, listed with binomial names.

By the time Linnaeus died it was the norm for expeditions around the world to take a botanist with them, hence CHARLES DARWIN’s famous voyage on the Beagle.

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DANIEL BERNOULLI (1700- 82) JAMES CLERK MAXWELL (1831- 79)

1738 – Switzerland
1859 – England

‘Gases are composed of molecules which are in constant random motion and their properties depend upon this motion’

The volume of a gas is simply the space through which molecules are free to move. Collisions of the molecules with each other and the walls of a container are perfectly elastic, resulting in no decrease in kinetic energy. The average kinetic energy of a gas increases with an increase in temperature and decreases with a decrease in temperature. The theory has been extended to provide a model for two states of matter – liquids and solids.

Bernoulli had a great advantage over DEMOCRITUS. He knew that free atoms were more than simply tiny grains flying though space; they were tiny grains flying through space and obeying NEWTON’s Laws of Motion.
Bernoulli proposed a ‘bombardment theory’, which stated that a gas consisted of tiny particles in rapid, random motion like a swarm of angry bees. He realized that in the case of such a gas visualized as a host of tiny grains in perpetual frenzied motion, the atoms hammering relentlessly on the walls of any containing vessel would produce a force by bombarding the container. The effect of each individual impact would of course be vanishingly small. The effect of billions upon billions of atoms, hammering away incessantly, however, would be to push the walls back. A gas made of atoms would exert a jittery force that we would detect as a ‘pressure’.

Heating a gas would make its particles move faster.
The pressure of a gas such as steam was easy to measure using a piston in a hollow container. This was essentially a moveable wall. To deduce how the pressure of a gas would be affected by different conditions, Bernoulli first made some simplifying assumptions. He assumed the atoms were very small compared to the gulf between them. This allowed Bernoulli to ignore any force – whether of attraction or repulsion – that existed between them, as being unlikely to be ‘long range’. (This is an ‘ideal’ or ‘perfect’ gas. The behaviour of a real gas may differ from the ideal, for example at very high pressure). With the motion of each atom unaffected by its fellows, Newton’s laws dictated that it should fly at a constant speed in a straight line. The exception was when it slammed into a piston or the walls of the container. Bernoulli assumed that in such a collision a gas atom bounced off the walls of the surface without losing any speed, in the process imparting a miniscule force to the wall.

What would happen if the volume of the gas were reduced by applying an outside force to the piston? If the gas were reduced to half its original volume, the atoms would now have to fly only half as far between collisions, in any given time they would collide with the piston twice as many times and would exert twice the pressure. Similarly, if the gas were compressed to a third of its volume, its pressure would triple. This had been observed by ROBERT BOYLE in 1660 and named Boyle’s Law.

What would happen to the pressure of gas in a closed cylinder if the gas were heated while its volume remained unchanged? Exploiting the insight that the temperature of a gas was a measure of how fast on average its atoms were flying about, that when a gas was heated, its atoms speeded up, he deduced that as the atoms would be moving faster they would collide with the piston more often and create a greater force. Consequently the pressure of the gas would rise. This was observed by the French scientist JACQUES ALEXANDRE CESARE CHARLES in 1787, and christened Charles’ law.

After 120 years MAXWELL polished Bernoulli’s ideas into a rigorous mathematical theory. In Germany, LUDWIG  BOLTZMANN championed the atomic hypothesis, but was refuted by the Austrian ERNST MACH, who was convinced that science should not concern itself with any feature of the world that could not be observed directly with the senses.

BERNOULLI’S PRINCIPLE

‘As the velocity of a liquid or gas increases, its pressure decreases; and when the velocity decreases, its pressure increases’

At a narrow constriction in a pipe or tube, the speed of a gas or liquid is increased, but its pressure is decreased, according to Bernoulli’s principle. This effect is named the Venturi effect (and a pipe or tube with a narrow constriction the Venturi tube) after the Italian G.B. Venturi (1746-1822) who first observed it in constrictions in water channels. An atomiser works on the same principle.

 

The principle is expressed as a complex equation, but it can be summed up simply as the faster the flow the lower the pressure.

An aircraft wing’s curved upper surface is longer than the lower one, which ensures that air has to travel further and so faster over the top than it does below the wing. Hence the air pressure underneath is greater than on top of the wing, causing an upward force, called lift.

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ANDERS CELSIUS (1701- 44)

1742 – Sweden

‘The temperature difference between the freezing point and the boiling point of water is a hundred degrees’

portrait of ANDERS CELSIUS (1701-1744) ©

ANDERS CELSIUS

The scale was called centigrade but was renamed Celsius in 1969

In the fahrenheit scale introduced by the German-Dutch physicist DANIEL GABRIEL FAHRENHEIT the freezing point of water is set at 32 degrees and the boiling point at 212 degrees. Fahrenheit’s scale has been superseded by the metric Celsius scale, with water freezing at 0degrees C and boiling at 100degrees C

A conversion can be made from Fahrenheit to degrees Celsius by subtracting thirty-two and multiplying this figure by five and dividing by nine.

The kelvin scale is preferred

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BENJAMIN FRANKLIN (1706-1790)

1752 – The New World

Portrait of BENJAMIN FRANKLIN ©

BENJAMIN FRANKLIN

‘If you would not be forgotten when you are dead and rotten, either write things worth reading, or do things worth writing about’

Curious about how just about everything works, from governments to lightning rods, Franklin’s legacy, in addition to the many inventions such as lightning conductors, bifocal lenses and street lamps, was one of learning. He established one of the first public libraries as well as one of the first universities in America, Pennsylvania. He established the Democratic Party. Franklin was one of the five signatories of the Declaration of Independence from Great Britain in 1776 and was a later participant in the drafting of the American Constitution.

‘Benjamin Franklin’s choice for the signs of electric charges leads to electric current being positive, even though the charge carriers themselves are negative — thereby cursing electrical engineers with confusing minus signs ever since.
The sign of the charge carriers could not be determined with the technology of Franklin’s time, so this isn’t his fault. It’s just bad luck’

Franklin was a pioneer in understanding the properties and potential of electricity. He undertook studies involving electric charge and introduced the terms ‘positive’ and ‘negative’ in explaining the way substances could be attracted to or repelled by each other according to the nature of their charge. He believed these charges ultimately cancelled each other out so that if something lost electrical charge, another substance would instantly gain the same amount.

 

His work on electricity climaxed with his kite flying experiment of 1752. In order to prove lightning to be a form of electricity, Franklin launched a kite into a thunderstorm on a long piece of conducting string. Tying the string to a capacitor, which became charged when struck by lightning, vindicated his theories.

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