Torricelli saw that, rather than being sucked upwards by the vacuum, the water was pushed up the vertical pipe by the weight of the atmosphere pressing on the water at the bottom of the well. The vacuum was essentially an absence of atmosphere: so the water rose until the weight of the water in the vacuum section of the pump equalled that of the atmosphere acting on the water in the well. The vacuum was held in balance by the weight of water and the counteracting weight of the atmosphere.
Torricello realised that, if this were true, then a heavier liquid would rise to a lower height than the ten metres achieved by the water, and when, in 1643, he and his pupil Vaviani tested the effect of a vacuum on a column of mercury they found that it rose just 80 cm. In doing so he invented the mercury barometer, but more important, this seemed to support his theory.
When the French philosopher Blaise Pascal heard about Torricello’s mercury column he took the experiment a step further. He suggested that the weight of the atmosphere at sea level should be greater than at high altitudes, and as Pascal was living in the low-lying Normandy city of Rouen, he asked his brother-in-law, Florin Périer, to test his hypothesis. On 19 September 1648 Périer climbed the 1,500-metre Puy de Dôme near Clermont-Ferrand carrying a glass tube containing mercury. Sure enough, on reaching the summit, the mercury had risen by just 71 cm, 9 cm less than at sea level – this was proof that the weight of the atmosphere diminished with height.
While Otto von Guericke of Magdeburg was probably unaware of Torricello’s work, he was also fascinated by the effects of vacuums. In an early experiment he pumped air out of a copper sphere, and was surprised at the force of air that rushed in when he opened a tap in its side. Encouraged by this he then placed two copper hemispheres together, connected only by an airtight seal, pumped the air out of them and then challenged two teams of horses to pull them apart. They failed, showing the extraordinary power generated by a vacuum inside a vessel. Guericke’s next experiment, conducted in the 1650s, showed this power not just as a passive resistance, but as a powerful dynamic force. First, he built a metal cylinder with a tightly fitting piston. A group of men then pulled on a rope attached to the piston rod, thereby creating a partial vacuum in the cylinder. Guericke now connected a sphere, which held a vacuum, to the cylinder and opened a valve between them. The small amount of air that was left in the cylinder rushed into the vacuum in the sphere and the piston was sucked inwards, overpowering the best efforts of twenty men to prevent it. The creation and destruction of a vacuum could generate power previously unknown to humanity.
In the 1660s the English scientist Robert Boyle toured Europe where he learned of the work of Torricelli, Pascal and Guericke. His work on gases became the foundation of a new science but his experiments also required improved devices for pumping air, which he developed. Other experimenters too looked for better ways to create a vacuum. Sir Samuel Morland, Christiaan Huygens and the Frenchman Jean de Hautefeuille all experimented with using gunpowder to blow air out of a cylinder, but the most significant step was taken by Huygens’s French assistant Denis Papin.
Papin was a Huguenot who had left his native France in 1675 to make a career as a scientist and inventor in England. In common with his predecessors he understood that the creation of a vacuum provided a source of power. Sometime between 1690 and 1695 Papin abandoned the idea of a gunpowder charge and instead placed a small amount of water in the bottom of a cylinder, with a piston at the top. He heated the water, which drove the piston upwards, and the resulting steam pushed most of the air out of the cylinder. When the fire was removed, the steam condensed and the piston was pulled down by the resulting vacuum and the weight of the atmosphere. Papin thus hit upon the two applications of steam that were to drive the Industrial Revolution – the ability of steam to create a vacuum, as used by Thomas Newcomen and James Watt in their atmospheric engines, and the pushing force of steam under pressure, which would drive Richard Trevithick’s locomotives.
The story of steam before the great breakthrough by Thomas Newcomen culminates in the figure of Captain Thomas Savery, a wealthy gentleman from Devon with a keen interest in mechanical devices. On 25 July 1698 Savery was awarded a fourteen-year patent for ‘Raising water by the impellent force of fire’, which was extended in 1699 for a further twenty-one years. Savery’s apparatus was a pump rather than an engine, but it was the first steam device known to have been used on a large scale. The pump was not an experimental model nor a playful garden ornament but a practical device for taking water out of mines, a problem that bedevilled the coal and metals miners of Britain.
The pump had no moving parts other than valves and used both properties of steam that we have been tracing: its use in creating a vacuum, and the power of steam working under pressure.
Savery pump: Firstly steam was sent from a boiler into a vessel called a receiver. Once filled with steam the valve between the two was shut off and cold water was poured over the outside of the receiver. This condensed the steam inside and created a vacuum. A different valve was then opened on a pipe leading from the receiver down to the water in the mine. The presence of the vacuum caused the water to be forced up the pipe, which could then be closed off. The next stage was to force the water now in the receiver up through a third pipe and out of the mine. This was done by sending yet more steam into the receiver from the boiler and opening a valve in the third pipe to allow water to be expelled under the pressure of the steam. The process of sealing off the receiver and condensing the steam was then begun again.
Savery improved his pump in 1699 by using two receivers working alternately from the same boiler: he then developed it further by using a wheeled valve so that when one receiver was open the other was closed. His 1702 book The Miner’s Friend revealed the final improvements – a sector plate in the shape of a fan, which was later adapted by Newcomen and Watt to automatically open and close steam valves. He also added a second ‘feeder’ boiler to keep the so-called ‘great boiler’ continually topped up with water via a clack (or one-way) valve. Savery could have omitted the third phase of the process (in which steam is driven upwards under pressure) and simply allowed the water to be drained off at the level of the receiver, but he would have faced the same problems as Torricello in Florence – the water forced up the original pipe would never be lifted more than thirty feet or so.
The use of steam under pressure had its dangers, as John Desaguliers later described in 1744: ‘I have known Captain Savery, at York Buildings make steam eight or ten times stronger than common air; and then its Heat was so great that it would melt common soft Solder; and its Strength so great as to blow open several of the Joints of his Machine; so that he was forc’d to be at the Pains and Charge to have all his Joints solder’d with Spelter or hard Solder.’6
The Savery pump was installed in a few mines, but without much success. The need to heat and cool the receiver during every cycle made it slow and inefficient and it found wider use in the ornamental gardens of the nobility. In 1729 the garden designer Stephen Switzer commented: ‘How useful it is in gardens and fountain works ay or might have been seen in the garden of that right noble peer, the present Duke of Chandos, at his late house at Sion Hill, where the engine was placed under a delightful banqueting-house, and the water being forced up into a cistern on the top thereof, used to play a fountain contiguous thereto in a very delightful manner.’7
The duke’s guests might have been less delighted if they had known that, for all his engineering ingenuity, Savery had never come up with a safety valve.
Despite their failure as pumps for draining mines, Savery pumps were adapted for other uses – they were made until the 1760s, and were still in use in the early 1800s. Developers got round the problem of high-pressure steam by using the pumps only as suction devices, with the water that was pulled into the receiver being drained into a cistern that could then drive a waterwheel. Joshua Rigley of Manchester built this type of pump in Lancashire in the 1760s, while in 1827 John Farey described an adapted S
avery engine driving lathes at a works in St Pancras. But the real importance of the Savery pump comes from its proximity to its successor, the Newcomen engine.
7. The Newcomen Engine
HOWEVER MUCH WE are able to trace the development of steam power through the preceding centuries, and however much ingenuity was shown by the likes of Worcester, Papin and Savery, the engine developed by Thomas Newcomen was such a bold and brilliant advance that it deserves a place among the greatest inventions in human history. Not only did Newcomen show great technical imagination and flair, he also worked tirelessly to make his invention into a practical working engine. This was the first machine that replaced human, animal and water power; its effect on the world could hardly have been greater.
Little is known about the life of Thomas Newcomen. His father Elias was a freeholder in the town of Dartmouth in Devon, but there is no documentary evidence of his working life. Thomas was born in Dartmouth and christened on 24 February 1664 – birth records were not commonly kept but it is fair to assume that he was born in January or February. His family were Nonconformists, probably Baptists, and had connections with the scholar John Flavel of Bromsgrove, a place that was to feature in Newcomen’s career. The historian Thomas Lidstone (1821–88) wrote three pamphlets about Newcomen and included the fact that he was apprenticed to an ironmonger in Exeter, but no record of this has been found.1
When aged twenty-one Newcomen is likely to have completed his apprenticeship and returned to Dartmouth. We know from contemporary accounts that he set up business with his fellow devout Baptist John Calley (sometimes known as Cawley) in the ironmongery trade. Newcomen married in 1705 and his son Elias was born the following year – he would later take on his father’s business. In 1707 Newcomen took a lease on a large house where he conducted his ironmongery business, with part of it used as a place of worship; by this time he had become the preacher of the local Baptist congregation.2 While the house was the base of the business it seems that Newcomen and Calley used a nearby workshop for the practical side of their work, and it was here that they carried out their experiments with steam and built their prototype engines. Calley was a plumber and glazier, Newcomen a blacksmith–ironmonger. This term described the making and repair of more or less anything made of metal including tools, receptacles, fire irons and the like, but possibly also more sophisticated instruments and guns.
So how did Newcomen, a Dartmouth ironmonger, become interested in steam power? We can only speculate, but his proximity to the tin and copper mines of Cornwall and Devon may have been crucial. He certainly visited the mines in the course of his business (he also travelled the locality as a Baptist preacher) and knew the problems they had with drainage. There may have even been a Savery pump working in one of these mines, but although Savery and Newcomen came from the same county there is no evidence that they met before Newcomen had built his engine. Suggestions by nineteenth-century historians that Newcomen knew about Papin’s and Worcester’s work or that he was in correspondence with Robert Boyle have all been discounted; the likelihood of a Devon tradesman reading the Philosophical Transactions of the Royal Society is indeed negligible. It may have seemed unbelievable to Victorian historians that an untutored artisan could have made such a groundbreaking invention without the help of scientists and aristocrats – but in that sense he was more typical than they knew.
In fact Newcomen did not follow in direct line from any of his predecessors; he took findings from each (while unaware of their origins) and created something quite different. It is clear that the problem of water in mines was sufficiently pressing to engage a number of people, so it is perhaps not surprising that developments happened in parallel. And while we can make reasonable conjectures as to why Newcomen became interested in solving the problem using steam power, there is no explanation for his extraordinary dedication to making a working engine. Newcomen simply embodied that necessary combination of inspiration and perspiration.
The most reliable witness to Newcomen’s work was a young Swedish engineer called Marten Triewald who came to England in 1716 – after the first Newcomen engines had been built – and stayed for the next ten years. He visited Newcomen and Calley in their workshop and later helped to erect a Newcomen engine at Byker colliery near Newcastle, before himself building an engine at Dannemora mines after his return to Sweden. In 1734 he gave an account of the motivation behind Newcomen’s work:
Now it happens that a man from Dartmouth, named Thomas Newcomen, without any knowledge whatever of the speculations of Captain Savery, had at the same time also made up his mind, in conjunction with his assistant, a plumber by the name of Calley, to invent a fire-machine for drawing water from the mines. He was induced to undertake this by considering the heavy cost of lifting water by means of horses, which Mr Newcomen found existing in English tin mines. These mines Mr Newcomen often visited in the capacity of a dealer in iron tools with which he used to furnish many of the tin mines.3
According to Triewald and another contemporary writer, Stephen Switzer, Newcomen and Calley began serious work on their engine in 1698 at the latest. But the first fully working Newcomen engine was not installed until 1712 – so what happened in the intervening fourteen years? As we don’t have any documentary evidence, we have to make assumptions from the end result. It seems certain that both men worked part time on the idea while carrying out their normal business. And once Newcomen had conceived the central idea of the engine it is likely that they made scale models; while this was an essential step it could have caused problems due to the ‘scale effect’ whereby heat loss and friction are more exaggerated at small scale.
Newcomen’s first requirement when building a model was to have a cylinder and piston with a reliable seal. He probably used the seven-inch-diameter cast-brass pump cylinders that were common at the time, applied a leather seal round the piston head, and then put water on top of the seal to improve its resistance to leaks. It was a relatively simple process to introduce steam into the cylinder, but the next phase in the engine’s cycle required the steam to condense. To allow this to happen naturally (as Papin had done) would have been too slow for a working engine. It seems that Newcomen first poured cold water over the cylinder, as Savery had done on his pump. But he soon revised this method and instead built a jacket around the cylinder, through which he circulated cold water. This would have got the engine to work but probably not to a satisfactory level. Even with the beam and rods working in the right way the engine would have struggled to maintain a continuous action.
Though the cooling of the cylinder might seem a secondary matter compared to the generation of power, it was of fundamental importance. In fact the removal of excess heat from engines is still a prime concern of engineers: around 90 per cent of the heat in steam engines, and 70 per cent in internal combustion engines, is waste. Newcomen knew that the cooling needed to be both efficient and rapid, otherwise all his work would be in vain.
The next advance therefore was dramatic: Marten Triewald described (see capsule text here) how a pin-hole in the brass allowed cold water to shoot directly into the cylinder, creating an immediate vacuum and pulling the piston down with such force that it crushed the bottom of the cylinder sending water flying everywhere.
We can imagine the scene in the small workshop. Did Newcomen and Calley turn to each other, perhaps first in panic and amazement, and then with the realisation that they had, through their immense perseverance and ingenuity, stumbled on something extraordinary and transforming? Did they then pick through the pieces and discover how this had happened and immediately take steps to reproduce the ‘accident’ under controlled conditions? Something like that surely happened.
This was a happy accident but it never would have come about without the years of tenacity that preceded it. Newcomen still had to solve other fundamental problems, including how to rid the cylinder of the condensed steam (now water) and of the air that entered with the steam – he no doubt had to rebalance his beam in order to t
ake account of the different level of force, and later developed a system of rods and levers so that the engine operated its own valves automatically – but now he must have known that once he solved those technical problems, his engine would run continuously. Human labour was about to be replaced, for the first time in history, by a mechanical device driven by energy derived from the earth.
Writing in 1844, William Pole asserted that the first Newcomen engine was installed in Huel Vor mine in Breage, Cornwall, around 1710, but there is no documentary evidence of its existence.4 The first fully working commercial Newcomen engine that we can be certain about was erected in 1712 at Dudley Castle colliery; Newcomen had been introduced to the manager of the colliery by a fellow Baptist. This first engine was an extremely sophisticated machine in which all the essential technical problems had been solved; it even included a system of automatic valves. Marten Triewald tells us that: ‘The cylinder of this machine measured 21 inches in diameter and was 7 feet 10 inches high. The boiler was 5 feet 6 inches in diameter and 6 feet 1 inch high. The water in the boiler stood 4 feet 4 inches high and contained 13 hogsheads; besides, the machine delivered at every rise or lift (12 lifts in a minute) 10 English gallons of water, and the mine was 51 yards or 25½ fathoms deep.’5
Newcomen’s first engine: A metal cylinder [a] with a piston forming an airtight seal at one end and closed at the other, is filled with steam injected from a boiler [b]. Cold water is then injected into the cylinder via a valve [f], condensing the steam. The resulting vacuum pulls the piston down into the cylinder. The top of the piston is attached to one end of a balanced beam [i]; drawing the piston down pulls up the other end of the beam. When the vacuum is released the beam tilts back under gravity. The power is therefore provided by the force of the vacuum created when the steam in the cylinder is turned to water – which occupies only 1/1600th of its volume. This power in turn comes from the steam, which is heated by burning coal. This, therefore, was the first successful conversion of the thermal energy of coal into the mechanical energy of movement.
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