Skip to main content

Currently Skimming:

2. Conundrums
Pages 64-113

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 64...
... Only then did the vast factories of the 19th-century industrial revolution begin to appear. Fast-flowing water from mountain streams was no longer a requirement, but steam engines needed water in bulk 64
From page 65...
... Heat flowed, in some ill-defined sense, through a steam engine, yielding mechanical effort as it did so. It was not obvious that any heat was "used up" in the process.
From page 66...
... Then in 1824 he produced one of the most profound and original scientific works of his or any era. In pondering what went on inside a steam engine, Carnot's acute insight was to think in terms of a repeating cycle.
From page 67...
... He constructed a four-part cycle. First, the cylinder was charged with steam at the high temperature; second, the piston was released so that the charge of steam produced an amount of work, cooling and expanding as it did; third, spent steam was discharged at the low temperature; finally, the piston returned to the start.
From page 68...
... If the efficiency of the air engine was greater than the efficiency of the steam engine, it would be possible as before to move heat uphill without a net expenditure of work. Therefore the efficiency of the two engines had tO be the same.
From page 69...
... On top of that, he had grown up in an industrial city and, with his brother James, had made toy steam engines and other machines as a child. He failed to find a copy of Carnot's treatise in Paris, but he studied Clapeyron's paper and, during the Thomson family's summer outing at
From page 70...
... In the 1 860s the German scientist Hermann van Helmholtz visited William Thomson in Glasgow and while there met lames. He wrote to his wife that lames "is a level-headed fellow, full of good ideas, but cares for nothing except engineering, and talks about it ceaselessly all day and all night, so that nothing else can be got in when he is present.
From page 71...
... As William approached his final exams, James wrote to contrast his situation: "I wish my apprenticeship was as nearly done as yours, but even when it is done, I fear I shall have no such comfortable berth to step into as that which is probably waiting for you.
From page 72...
... Facing pressure from the BA and other new scientific groups, the Royal Society had by midcentury largely regained its former reputation. At the Oxford BA meeting, Thomson met lames Prescott Joule, an
From page 73...
... A visiting German scientist, Carl Jacobi, recalled speaking to the members of the Lit & Phil in 1842, when he "had the courage to say that it is the honour of science to be of no use, which provoked a powerful shaking of heads." While working in the family brewery, lames Joule began to do scientific experiments. His first project, perhaps motivated in part by the rapidly growing abundance of noisy, smoky steam engines in Manchester, was an investigation of electric motors (invented by Faraday in 1821)
From page 74...
... Over a period of years he satisfied himself of a fundamental principle: A certain quantity of mechanical work, when efficiently and completely transformed, always created an equivalent amount of heat. This conversion factor he named the mechanical equivalent of heat, and in the ungainly units of the day he concluded that a quantity between about 600 and 1,000 footpounds of mechanical effort was needed to heat one pound of water by one degree Fahrenheit.
From page 75...
... In the audience was the new Glasgow professor, William Thomson, who at this time was wholly persuaded of Carnot's principle that heat passed through a steam engine unchanged in quantity, creating mechanical work as it went. A Carnot engine running in reverse, therefore, used mechanical work to move a quantity of heat from a low temperature to a higher one, but now here was this man Joule saying that he could use mechanical work to create heat.
From page 76...
... ,, Looking for a temperature increase from the top to the bottom of a waterfall was a more hopeful than plausible way of finding out the heat generated by motion. Thomson's charming tale, recounted many years later, is a fine example of his capacity for embellishment.
From page 77...
... ,, Elizabeth and Anna had tried teaching their brothers to dance when they were young, though at the time William in particular "professed utter scorn." lames never danced, but William evidently found a taste for
From page 78...
... Elizabeth had married the Reverend David King in 1843, and they lived elsewhere in the city. The rest still lived with their father, looked after by their Aunt Agnes Gall.
From page 79...
... A letter from him to William survives, written in April 1885 on notepaper of the Colonial Mutual Life Assurance Society in Melbourne. It is a brief letter of introduction to William Sir William Thomson by then on behalf of a Melbourne colleague of Robert's who was coming to England for some months.
From page 80...
... At Liouville's prompting, Thomson wrote a short proof of the equivalence of Faraday's lines of force and the inverse square, action-at-a-distance picture preferred by the French. Now equipped with Green's resurrected mathematics, he developed to a high degree of sophistication a new geometrical account of electric forces and charges.
From page 81...
... Likewise, Thomson showed, the conducting surface of an electrically charged body can be related to a set of charges with the appropriate arrangement and calculating from a finite number of points is easier than dealing with an extended body of arbitrary shape. Back in Cambridge, Thomson talked of his ideas at the British Association meeting there in rune.
From page 82...
... Faraday, joining it in early 1810, when he was 18 years old, participated nervously at first in discussions of history, philosophy, and science. Not unlike William Thomson's father, Michael Faraday was single-minded in the task of self-improvement.
From page 83...
... Their social life was almost wholly among the Sandemanians. Faraday avoided as far as possible civic events and functions, even if he was the object of the honor, and in later years almost his only concession to the social graces was his annual attendance of the anniversary dinner of the Royal Institution.
From page 84...
... 84 work in company, or think aloud, or explain my thoughts at the time. Sometimes I and my assistant have been in the laboratory for hours and days together, he preparing some lecture apparatus or cleaning up, and 1 1 1 1 1 scarcely a word has passed between us.
From page 85...
... His most celebrated discovery was probably his demonstration of electromagnetic induction. It had been known since 1820 that a current passing along a wire would make an adjacent compass needle deflect.
From page 86...
... His conception of magnetism, qualitative though it was, yielded quantitative predictions. William Thomson first encountered Faraday's science in the early 1840s, when he was taking classes in Glasgow from David Thomson, substituting for the ailing Meikleham.
From page 87...
... A compass needle deflected by a current passing along a wire, for example, might flick to the left above the wire but to the right below. The geometry of magnetic forces, Thomson showed, paralleled a mathematical description of a localized twist or rotation of the elastic medium (as if, loosely speaking, one held a lump of gelatin in one hand, stuck a fork in it with the other, and twisted the fork a little)
From page 88...
... Since the same medium, he hoped, would eventually be seen to carry both kinds of effects, there was the ultimate prospect of connecting electricity and magnetism by means of a single fundamental theory. This was to be the preoccupation of a lifetime, but for the moment Thomson contented himselfwith working out a couple of long accounts of the geometry and mathematics of magnetic forces, as he had done for electricity.
From page 89...
... He arranged to have testimonials sent to the Glasgow faculty but immediately regretted doing so. A month after lames Thomson's death he wrote to William to explain that after consulting his older brother he decided he could not go through with the application.
From page 90...
... Stokes wrote voluminously on mathematical physics, ended up with a theorem,4 an equation in fluid mechanics, and some optical phenomena named after him, served for a long time as secretary of the Royal Society, oversaw in minute detail the production of the society's Pro ceedirlgs, and acted, through his indefatigable correspondence, as a guide and mentor to numerous mathematical physicists in Britain, Thomson included. That this career was lost to Glasgow University because of an antiquated rule might have been, in Professor lames Thomson's hand, an additional spur to long overdue reform.
From page 91...
... Science, he explained, began with natural history, which was the close observation and classification of material phenomena, and rose to the level of natural philosophy, which was the attempt to understand and connect those phenomena by rational means, expressed ultimately in the language of mathematics. Mechanics was the most mature of sciences, while electricity and magnetism were approaching that pinnacle.
From page 92...
... As a professor of natural philosophy he deserves credit for one fundamental innovation, which was the teaching of practical science through student experimentation. With his brother lames he had made mechanical toys, but not until his visit to Paris did he attempt any measurement or manipulation in a scientific laboratory.
From page 93...
... This became an essential part of his course in natural philosophy. He did not merely teach mathematical methods and explain what crucial information had emerged from experiments by others.
From page 94...
... With his father and brother John dead, both sisters married and, after 1851, brothers lames in Belfast and Robert gone to Australia, William Thomson was alone in the old family home except for his aunt and housekeeper, Agnes Gall. He went to dances with lemima Blackburn, Hugh's wife, as chaperone.
From page 95...
... " By this time, however, she had seen young William Thomson evolve, over the decades, into the wealthy and celebrated Lord Kelvin, a great figure in the land. This may have amplified Sabina's remorse.
From page 96...
... Hermann van Helmholtz, encountering her for the first time, wrote of "a rather pretty woman, very charming ancl intellectual" ancl the novelist William Thackeray, having met the Thomsons in Glasgow through mutual friencls, askocl to "give my best regards to .
From page 97...
... CONUNDRUMS 97 Thomsons went on a Mediterranean tour, taking in Gibraltar, Malta, and Sicily. To William, long accustomed to hiking in the highlands, this was a mere jaunt, but Margaret wore herself out, came home weak and ill, and though the nature of ailment remains unclear she was an invalid for the rest of her life.
From page 98...
... After three years of thinking mostly about electricity and magnetism, Thomson returned to his Paris discovery of the science of steam engines. Still he had not seen Carnot's essay and knew it only through Clapeyron.
From page 99...
... Gas thermometers, therefore, gave slightly different temperature scales depending on which gas was used. One scale could always be calibrated against another, but since there was no independent way of measuring temperature, there was no way to say which temperature was most nearly correct that is, which one corresponded most closely to the temperature implicit in the ideal gas law.
From page 100...
... Carnot had established that the maximum work any engine can produce from a known quantity of heat can depend only on the upper and lower temperatures between which the engine cycles, and that this efficiency is the same no matter what the working substance, whether steam, air, or some other gas. Thomson defined a temperature scale by asserting that a Carnot cycle operating through a one-degree interval always produced the same amount of work from a given quantity of heat.
From page 101...
... He persisted with Carnot's view that the production of mechanical work during a cycle came from the transmission of heat from a higher to a lower temperature. But in a footnote he referred to "Mr.
From page 102...
... Even as he was preparing his account of Carnot, Thomson's grasp of this new science evolved in fits and starts. Writing to Forbes, he teasingly mentioned that he had thought up a trick for producing ice "act li~itum without the expenditure of mechanical effect." A Carnot engine running in reverse moved heat from a lower to a higher temperature.
From page 103...
... A bar of metal, he noted, will conduct heat from a hot body to a cooler one without producing any mechanical work, whereas passage of the same amount of heat through a Carnot engine willproduce work. Carnot himself had at least indirectly made the same point, but either was not troubled by it or left it as a matter for later consideration.
From page 104...
... His solution seems ludicrously simple, not to say obvious. In a Carnot cycle, he argued, some of the heat passes from hot to cold unchanged, but some is converted into work.
From page 105...
... In that case he sifted what was important and necessary from what was extraneous and incidental, and reconciled the two views. In the case of Carnot and Joule, he could not see beyond the apparent contradiction to the underlying consistency.
From page 106...
... Nevertheless, having made heat explicitly a kind of atomic motion, Rankine found it obvious that heat could turn into mechanical work, since both were merely different kinds of motion. Rankine reached the same conclusions that Clausius did about the proportion of heat converting into work in a Carnot cycle.
From page 107...
... With the recognition that an engine converted heat into work, discussion of the efficiency of that conversion became a separate Issue. Thomson stated the second principle thus: "It is impossible, by means of inanimate material agency, to derive mechanical effect from any portion of matter by cooling it below the temperature of the coldest of the surrounding objects." That is, a machine can derive work when temperature flows from hot to cold; it can't produce work by making some object colder than everything else.
From page 108...
... Carnot had recognized that a reversible engine gives maximum efficiency, but he had apparently not stopped to wonder about the fate of the heat lost, through conduction or escaping steam, in a less efficient and therefore irreversible engine. In an irreversible process, 7 Uber die Erhalt?
From page 109...
... But there were two significant differences. First, the revised temperature corresponded to the temperature defined by an ideal gas thermometer and was therefore closely related to the practical temperature scales that laboratory scientists had long used.
From page 110...
... It is a tribute to the power and thoroughness of his reasoning that he could deduce the existence of an absolute zero without any reference to the physical nature of heat itself. He used only what was known empirically of heat's properties.
From page 111...
... He developed the full theory of Carnot engines only after Clausius had supplied the essential idea that heat was consumed, not just transferred from one place to another. He made use of a quantity that eventually became entropy but did so apparently without seeing the general utility of it, as if he found it convenient for a specific purpose but failed to look beyond.
From page 112...
... as well as an ability tO synthesize arguments and evidence into a coherent whole. Helmholtz had come to Britain in 1853 and made a trip to Scotland, before attending the British Association meeting in Hull, in order to search out Thomson.
From page 113...
... He had established theorems in applied mathematics, extended Fourier's studies of the flow of heat, clarified the relation of electric charges and magnets to the forces they produced, as well as the interaction of magnetism with currents, and done as much as anyone to establish the foundations of classical thermodynamics. No other scientist in Europe at the time could lay claim to such range and depth of achievement.


This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More information on Chapter Skim is available.