Talk:Pound (mass)

Is "pound" a force or a mass (with reliable sources)...

Some of this is taken from discussion on the Wikipedia science reference desk http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Science/2011_June_1#Pound-mass_and_pound-force.3F and also on the talk page for Slug (mass).

From one of my aeronautics textbooks, "at the surface of the earth, an object with a mass of 1.00 kg weighs 9.8 N or 2.205 lb, and an object with a mass of 1.00 slug weighs 32.17 lb or 143.1 N". The textbook is: Shevell, R.S. (1989) "Fundamentals of Flight", 2nd Ed, Prentice-Hall. The quoted statement is on page xix in the section titled "Conversion Factors between SI Units and English Units".

In Niu's "Airframe Structural Design", 2nd Ed (http://www.amazon.com/Airframe-Structural-Design-Information-Structures/dp/9627128090), on page 599 a unit conversion table shows a pound (lb) as a mass of "U.S. Customary Unit" equal to 0.4536 kg. Perhaps the confusion isn't about the system of units, but rather their origin. Perhaps (unverified) a pound is treated as a force in English FPS units and as a mass in US FPS units? This wouldn't surprise me, as the US and UK/English can't agree on another unit of mass, being the Ton. Fortunately they both seem to agree that a ton is a mass, just of different values.

In Gere's "Mechanics of Materials", 5th Ed inside the front cover, pound (lb) is tabulated as a force of U.S. Customary Unit equal to 4.44822 N. Even if numerically correct, I guess if the textbooks can't agree whether "pound" is a mass or a force it makes it a bit hard to define.

The U.S. Electronic Code of Federal Regulations (e-CFR) Title 14 (Aeronautics and Space), Subchapter C (Aircraft), PART 23—AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES, Section 23.397 (Limit control forces and torques.) specifies forces in pounds (lbs). Refer http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=17ff3d50f518bbb3a2472296a8435378&rgn=div5&view=text&node=14:1.0.1.3.10&idno=14#14:1.0.1.3.10.3.71.27

Appendix 4 of Houghton, E.L. & Carpenter, P.W. "Aerodynamics for Engineering Students" considers the pound to be the fundamental unit of imperial mass, where 1 pound = 0.453 592 27 kg (page 572).

Perhaps all we can do in a Wikipedia article is highlight its ambiguity as either a mass or a force, with conversion factors accurate on Earth's surface.

Highlighting the system of units to which pound-mass belongs (FPS gravitational) would also be helpful to clarify difference between use in engineering and absolute FPS systems of units. There is a table at Pound-force that highlights differences between systems of units, but the whole table needn't be copied to Pound (mass). Just mentioning the FPS gravitational system of units at Pound (mass) I think would be sufficient. I would guess that many readers are unfamiliar with the various systems, as I was, so highlighting that a pound isn't always a pound and that it depends on what system of units you're using might help stop the argument about whether a "pound" is a force or mass. Also, as shown above, it seems that textbooks can't agree on the "mass" or "force" terminology (though luckily conversions still work out correctly, on Earth's surface anyway).

I'm not sure exactly how the Pound (mass) article can be written to improve its clarity but someone with more experience as an editor might be able to come up with something that takes info from all reliable sources. There seems to be a fair bit of heresay and useless bickering (almost religious zealotry) in this talk page. Why must a "pound" be defined as either a mass or a force? Perhaps lets just call it an "ambiguous unit of weight", or at least put some sort of disputed flag against the article if the bickering is to continue indefinitely. As long as the article remains in its present form however, reader confusion will continue. 203.129.23.146 (talk) 06:27, 5 June 2011 (UTC)

I don't know where this stupid notion that the pound is primarily a unit of force and needs to be renamed for use as a unit of mass comes from, but when it is actually being taught at university level I guess we can't ignore it, and it sure seems to be causing a lot of grief by confusing people about the simplest things. Fact is that a pound is defined legally as precisely 0.45359237 kilograms. Since there is no ambiguity whatsoever about the kilogram – it has always been a unit of mass and nobody claims otherwise – there can be no doubt that this legal definition makes the kilogram a unit of mass. This agrees with historical usage from before the difference between mass and weight-force was known, in which the pound was also obviously a unit of mass, as there were physical "weight" standards and no corrections for different gravity were made when moving them. But the quotation in the article slug (mass) suggests that at some point physicists using the FPS system decided they wanted it to be a unit of force instead. Maybe to match the similarly odd practice of using the term "weight" for the force rather than the mass?

I think the sources of confusion can be summarised neatly as follows:

• "Weight" is an ambiguous term. Physicists and engineers use it to refer to a force. Everybody else, including many legal standards documents, use the same term to refer to mass. Neither usage is more correct than the other. Every use of the word must be interpreted in context.
• The FPS system is not really a system of units in the strict sense but uses the "pound" ambiguously. Consequently there are really two consistent FPS systems. One is based on the pound-mass (0.45359237 kilograms) and introduces the poundal as a unit of force. The other is based on the pound-force (0.45359237 kiloponds) and introduces the slug as a unit of mass. The conversion factor between the pound-mass and the pound-force is the same as that between the kilogram and the kilopond: the standard gravity of precisely 9.80665 m/s² = 9.80665/0.3048 ft/s², or roughly 32.174 ft/s². Using pound-mass + poundal or slug + pound-force hides the conversion factor (1 pound-force = 1 slug × 1 ft/s²; 1 poundal = 1 pound-mass × 1 ft/s²) and makes the location-dependent constant appear where it belongs: 1 slug exerts a force of 32.174 pounds-force. 1 pound-mass exerts a force of 32.174 poundals.

In the metric system there is no such ambiguity, and consequently there is no subjective need for a unit of mass equal to 1 kg/9.80665 (the mass that causes a force of 1 Newton, analogous to the slug). On the other hand, "the same force that is exerted by the standard gravity of a kilogram" does exist as the kilopond, a rare and obsolescent unit analogous to the poundal and not really part of the metric system. Hans Adler 07:39, 5 June 2011 (UTC)

PS: You may be interested in this source, especially the section "Mass v. weight". To quote:

I suspect that there is a difference between British and American use. The British obviously decided that if they were going to buy apples on the Moon, then they wanted a pound of apples to contain the same number as on Earth, so it should be mass. The Americans said rather that they wanted a pound of apples to feel the same on the Moon as the Earth, so it should be force. Personally, I refuse to buy a slug of apples wherever I am!
A further American [correspondent's] comment: "In my experience, the folks who insist that pounds are always a unit of force tend to be the physics students (probably to make F=m*a easier on first-semester students) while the engineering students will use pounds more as a mass. Ultimately, Congress defined the pound in terms of grams (not newtons) in the 1890s, and in the 1950s the remnants of the foot/pound using world got together and standardized on the same number of grams, so 'pound' is definitely a unit of mass. Of course, there's still 'pounds of force' used, abbreviated 'lbf', but that has to be differentiated from 'regular pounds.' The slug, as I mentioned before, is simply a convenient unit to use so that it takes 1 lbf to accelerate it 1 ft/s2. " I must point out that Physics students in Britain did not use pound as a unit of force! Nowadays, they all use metric.

I don't know what qualifications the author has, but this has been a pretty prominent page on the topic for a while, and he seems to have received a lot of feedback. It is easy to confirm that British, American and international standards organisations agree in defining the pound in terms of kilograms, not kiloponds or Newtons, that scales which actually measure force rather than weight must be adjusted (using reference weights) when taken to a place with (slightly) different gravity, and that beam balances and their weight pieces are never adjusted in this way. The idea that the pound is "really" a force and the other usage is incorrect appears to function as a shibboleth in the same way that some misconceptions about English usage (such as the absolute split infinitive prohibition) are routinely spread by teachers even though they are demonstrably wrong. Hans Adler 08:09, 5 June 2011 (UTC)

See also NIST Federal Standard 376B (preferred metric units for general use by the government), which says in footnote 2 on page 2: "In commercial and everyday use, and in many technical fields, the term 'weight' is usually used as a synonym for mass. This is how 'weight' is used in most United States laws and regulations." And on page 13:

NOTE: There is ambiguity in the use of the term "weight" to mean either force or mass. In general usage, the term "weight" nearly always means mass and this is the meaning given the term in U.S. laws and regulations. Where the term is so used, weight is expressed in kilograms in SI. In many fields of science and technology the term "weight" is defined as the force of gravity acting on an object, i.e., as the product of the mass of the object and the local acceleration of gravity. Where weight is so defined, it is expressed in newtons in SI.

Shortly after this note, which makes it clear that the source is ultracareful about the mass/force distinction, conversions are given as follows:

• 1 slug = 14.59390 kg
• 1 pound = 0.45359237 kg
• 1 pound-force = 4.448222 N
• 1 poundal = 0.1382550 N.

Hans Adler 08:24, 5 June 2011 (UTC)

I don't know what you're hoping your insults will achieve. I've never claimed that the pound is "primarily a unit of force", simply that its not universally treated as a unit of mass and that confusion is possible. SI/metric is unambiguous, but that's because there is a single coherent system of units. If you have a look at the table at http://en.wikipedia.org/wiki/Pound-force#Foot-pound-second_systems_of_units you will see that there are three separate FPS systems in use. If you insist there are two perhaps you would care to correct this table. It is also used in other articles, including at Slug (mass). I'm not familiar with the FPS absolute system (with poundals as the unit of force) but the FPS engineering units are familiar to me (as an engineer). I don't deny your pounds to kg conversion (I don't think anyone has). You're all wrapped up in legalities, so perhaps you could cite the particular law that you refer to. If that law explicitly defines a pound as a mass (as opposed to a mere conversion to a mass) then you should put it in the article and it would sort out some of the bickering in this talk page. Your claim of the practices of scientists and engineers being "odd" is inappropriate and irrelevant. That you think it odd doesn't mean anything except that you are apparently unfamiliar with science and engineering, which doesn't offer you much credibility to judge either. The rest of your rambling is interesting, but seeminly irrelevant to my comment you replied to. You seem to be taking this very personally though. Why are you so insistent that pounds must be treated as a unit of mass and that anyone treating it as a force is stupid or odd? Are you claiming that the US Federal Aviation Administration that maintains the previously cited regulation that legally treats pounds as a force is stupid or odd? Is there really any harm in highlighting some of the ambiguities mentioned throughout this talk page (and others) in the article? You thinking them stupid, odd or simple doesn't make them irrelevent. The conversions at the end are appreciated, except they also belong in the article. Your apparent inability to comprehend conversion between mass and force is a little curious, though it may explain why you think scientists and engineers are odd. 203.129.23.146 (talk) 09:39, 5 June 2011 (UTC)

Also, quoting NIST documents is fine, but I wouldn't have thought what appears to be some guy's personal homepage (http://gwydir.demon.co.uk/jo/) really counts as a reliable source. I'm not implying what he says is wrong, but at least I went to the effort of quoting prescribed textbooks from university engineering courses. 203.129.23.146 (talk) 10:04, 5 June 2011 (UTC)

Answer

I don't know where this stupid notion that the pound is primarily a unit of force ... came from It comes from the fact in the near Earth surface gravitational field the distinction doesn't matter. One pound (mass) produces one pound (force) of weight. Gerardw (talk) 01:41, 6 June 2011 (UTC)

The distinction between a pound (mass) and a pound (weight) does matter in precise work since, even if you stay at sea level on the earth, the gravitational acceleration g can vary from about 9.78 to 9.83 m/s^2, a range of ~0.5% Cardamon (talk) 07:35, 6 June 2011 (UTC)

Which is not to say there is anything wrong the article -- I think it reads fine as it is. Gerardw (talk) 01:41, 6 June 2011 (UTC)

I am fully aware of that, of course. My problem is this: There was the word "weight", which referred both to the mass of an object and to its gravitational force. Etymologically, the word is more closely related to the force, but in common language it is most often used for mass. The unfortunate decision to go with the meaning of "weight" that was a better etymological fit rather than the more common one led to a split between physics terminology (weight = force) and common usage (weight = mass). My understanding is that this split did not happen in the same way for "pound", even though etymologically (as it comes from pondere, weighing) that would also have made sense. But the most precise way to measure "weight" was always by comparing it to a reference body. Some such reference bodies existed as physical standards. Taking them to extreme locations, one would not manipulate them in any way to account for the different gravity; one would instead adjust spring balances. So it was clear that, as defined by the standard, the pound was a unit of mass, not force.

As a result, the pound was no longer a unit of "weight" in physics terminology, although it still was in common usage. If you combine "the pound is a unit of weight" (true in common language), "weight is a unit of force" (true in technical language) and the engineering FPS system (with the pound-force rather than the pound as one of the fundamental units), and add to this the unfortunate though understandable practice of saying "pound" for "pound-force" in that context – then it is in fact easy to understand how the misconception of the pound as primarily a unit of force arose. But anyone teaching physics or engineering at university level should still have been aware of the underlying facts and should have understood that the pound is somewhat ambiguous but primarily a unit of mass.

Yet every few months we get an editor here who insists that the pound is absolutely a unit of force and nothing else, or, as in this case, that it is sufficiently ambiguous that it's POV to say it's primarily a unit of mass. As I said earlier, I consider this situation to be analogous to that of the split infinitive prohibition and similar misconceptions about English usage. Perfectly reasonable advice ("use force rather than mass as a base unit for engineering", "don't overuse split infinitives as they sometimes sound artificial", "sometimes leaving out an adjective can make your prose more crisp") has a tendency to get more and more extremist as it is passed from one generation of teachers to another ("the pound is a unit of force, in all contexts", "never use a split infinitive, ever", "never use an adjective, ever"). But often there is one influential teacher to whom one can point as marking the beginning of the extremism. In the case of language misconceptions it's Strunk and White, who severely overstated a lot of their advice, apparently never expecting that their readers would take them literally instead of following the excellent example they were setting with their own style. I was wondering if there was a similar event for pound-force extremism. Hans Adler 06:44, 6 June 2011 (UTC)

psi = pounds per square inch = common usage = force per unit area, and weight/weightless = common usage = difference in one's weight between being on earth and in space (only change of course being gravity) implies weight "could" (not must) also be considered force in common usage. also, you seem to have contradicted the table at Pound-force that details the fundamental units of three FPS systems (is it incorrect?). 203.129.23.146 (talk) 21:41, 7 June 2011 (UTC)

In common usage the distinction doesn't matter. Can you conduct an experiment in your residence that would distinguish between the mass and the weight of an object? If one accepts modern humans have existed for 50,000 years (see Human) and Galileo did his Tower of Pisa rock thing in 1589, it's only been 0.008 of the (chronological) existence of humans the concept that of these mass/weight concepts began to be understood.

Wiktionary gives the primary definition as force [1], Merriam-Webster says it's a unit of mass and weight. [2].

Ultimately, whether "pound" refers to mass, weight/force, cake, or the act of hitting someone or something, currency, a place to municipalities put stray dogs or illegal parked automobiles depends on context.

Therefore, confusion between the two concepts is understandable and opening a dialog with a description of a query or statement as stupid is both unwarranted and unwise. Gerardw (talk) 11:16, 6 June 2011 (UTC)

Someone else has (correctly) explained the context of "stupid" at WQA, so I will be content with just telling you that pounding on my choice of words is not really appropriate, either. Of course confusion between the two concepts is understandable. The problem arises when people take care not to confuse them, but make incorrect claims about the conventional meaning of words. I can understand how this happens to laypeople, but if such misconceptions are taught by books and teachers at university level, as was claimed at the reference desk by the anonymous user, then it's a problem. Hans Adler 11:50, 6 June 2011 (UTC)

Sorry to butt in here

but I've read dozens of books on weights and measures over the last twenty or thirty years. Unfortunately, I don't have them with me at this time, but here's the point. From everything I've read, governments throughout the world had weight standards that included sets of standard reference masses, i.e. "weights." This practice apparently goes back to the Bronze Age (e.g., Harappa, Mohenjo Daro, etc.). Also in use since ancient times was the balance scale, which, when used in conjunction with a standard reference mass, measures mass. Even if they didn't know the physics behind it (and of course they couldn't have) they had a de facto mass standard.

By the late 1700s, people in the Western world, at least, understood enough about physics that various national bureaus of weights and measures (now known as national standards institutes) began having the sort of discussions that we see here on this page, only perhaps more scholarly. As a result, by the time the USA adopted the English pound as a unit of mass in 1792, Thomas Jefferson was already reminding people of the difference between mass and weight, and explaining how the American pound is a unit of mass, and how in legal and commercial usage "weight" means "mass" in the physics sense.

In other words, you don't need to rely on a fine reading of NIST Handbook 130. You can go back to Jefferson and Franklin's original notes on the subject.

Or something like that. When I get around to it, I'll see if I can find some references.Zyxwv99 (talk) 02:57, 16 November 2011 (UTC)

I checked Jefferson's document Plan for Establishing Uniformity in the Coinage, Weights, and Measures of the United States. In that document he side-stepped the issue by refering to weights, not weight and only considering measurements using beam balance, not a spring balance. Of couse, in Jefferson's time the variations of gravity around the globe were understood - Jefferson himself being invovled in a discussion of where to site a pendulum that was to be used as a base unit of length. I seem to recall havign read that at some British weights were defined as being done at a specific temperature and air pressure. British legislators also talk about the kilogram being a "weight or mass". Martinvl (talk) 07:58, 16 November 2011 (UTC)

"Use in commerce"

The "use in commerce" section is written a bit strangely; in part because it probably doesn't belong here. I propose we move it to Mass versus weight. Mass versus weight. Gerardw (talk) 10:36, 12 September 2011 (UTC)

I'm not in favour of creating a new article if that's all that's going to be in it. The section is making the point that pound weight in commerce invariably means mass and this should rightly be in the article. However, I don't think that it is necessary or useful to quote the NIST document verbatim at length. A summary of its contents is all that is needed. SpinningSpark 17:57, 12 September 2011 (UTC)

Sorry, formatted link wrong. I'm referring to existing article. Gerardw (talk) 18:21, 12 September 2011 (UTC)

I agree, a summary of the section that was removed should be reinstated with references to the relevant publications and Wikilinks to Mass versus weight. Martinvl (talk) 07:19, 20 September 2011 (UTC)

the origin of Troy weight

I am changing this:

"The troy pound takes its name from the French market town of Troyes in France where English merchants traded at least as early as the time of Charlemagne (early 9th century). The system of Troy weights was used in England by apothecaries and jewellers."

to:

"The system of Troy weights was used in England by apothecaries and jewelers since the early 1400s, and became the official weight standard for coins in 1527."

I am deleting references to the myth that the troy weight system originated at Troyes (see Zupko, History of British Weights and Measures, p. 19). Zyxwv99 (talk) 02:33, 16 November 2011 (UTC)

I don't have Zupko, and the later(?) work by Connor and Simpson did assign the story credibility. It is more than plausible for the following reasons:

• Troyes was an important market place where English merchants are known to have traded.
• There are historical French references to a "marc de Troyes" (which would have been 8 ounces of a French Troyes pound), although unfortunately there is no indication of its precise weight.
• The French "poids de marc"/"livre de Charlemagne" standard (important historical artifact kept in Paris [3]) was close to the later Flamish "trooisch pond". (30.60 g / ounce vs. 30.76 g / ounce) and is therefore very likely related to the "marc de Troyes".
• The English troy pound (31.10 g / ounce) is roughly in the same area.
• According to two sources by Simpson and Connor which I cited in Apothecaries' system#Weight standards named after Troyes, a 14th century source reported the numerical relation between the English and French troy ounces to be exactly 64:63. Based on the modern troy pound of 31.10 g / ounce this would indicate a French troy pound of 31.61 g / ounce, i.e. up to rounding errors the historical national French weight standard, the "poids de marc"/"livre de Charlemagne".

I can find no reference anywhere to a book "History of British Weights and Measures" by Zupko, so I assume that you are referring to Zupko's "British Weights and Measures: A History from Antiquity to the Seventeenth Century" (1978) or one of his "dictionaries" (various publication dates until 1985). The acclaimed [4][5][6] work by Simpson and Connor is much later, and of course they were familiar with Zupko and (IIRC) cited him.

For the moment I will revert your edit. Of course if you can make a good case that Zupko may still have been right and that the later work by Connor and Simpson is not sufficient to suppress what he says, then per WP:NPOV we can give all the details, use more general language, or remove uncertain information. But you will have to provide a lot more detail of what Zupko actually says. Unfortunately I don't have any of his books. Hans Adler 09:27, 16 November 2011 (UTC)

I stand corrected and acknowledge that I was at least half-wrong. Here is the relevant text from Zupko:

The name for the new system probably came from the French marc of Troyes, but it is certain that the English Troyes pound did not come from Troyes, France. The Troyes marc had an ounce equal to 472.1 BI (British Imperial) grains. There was a family of pounds known as troy in the northern trade of the period whose ounces varied from 483 to 472 grains. (Footnote: Specifically, the Swedish mark-weight pund had an ounce of 483.3 BI grains; the Danish solvpund ounce, 481.5 BI grains; the Scots tron pound ounce, 481.1 BI grains; the Bremen pound ounce, 480.8 BI grains; the Norwegian skaalpund ounce, 477.4 BI grains; the Amsterdam pound ounce, 476.6 BI grains; the Scots trois pound ounce, 475.5 BI grains; the Dutch troy pound ounce, 474.7 BI grains; and the French troy pound (Troyes marc) ounce, 472.1 BI grains.) The English troy pound took its name, like the Scots and Dutch pounds, from the Troyes marc, but took its standard from some pound of full weight, probably the Bremen pound whose ounce weighed 480.8 BI grains.

--Zupko (1977), British Weights and Measures: A History from Antiquity to the Seventeenth Century, pp. 28-9

I intend to study the work of Connor and Simpson. In the meanwhile, I am glad others here are approaching this subject with the seriousness it deserved. Zyxwv99 (talk) 01:43, 20 November 2011 (UTC)

Wow. When I read Connor and Simpson to write the Apothecaries' system article, I knew that I was missing something because I could see fragments of one of Zupko's books on Google Books. But I couldn't get hold of any of the books, and I wasn't aware how much I was missing! Hans Adler 02:00, 20 November 2011 (UTC)

I should point out that whatever I say about the book by Connor and Simpson is from memory or from how I cited them in Wikipedia. I used a library copy when I was based in Leeds. Here in Vienna the library doesn't have it, but I consider buying it. Hans Adler 02:09, 20 November 2011 (UTC)

Ronald Edward Zupko's books tend to be available through inter-library loan.Zyxwv99 (talk) 02:35, 20 November 2011 (UTC)

Capitalization

There seems to be a little edit war going on here with regard to the capitalization of certain words: pound, avoirdupois, etc. I've tried doing some research on this, but don't feel qualified to answer the question. Britannica Online and NIST don't seem to use the capitalized forms, except when dealing with proper nouns, as in "In 1834, the British Imperial Troy Pound and Yard were destroyed by fire when the Houses of Parliament burned."

On the other hand, maybe there is an exception for when a word is preceded by the definite article and is the subject under discussion, as in "the Pound Avoirdupois is a unit weight currently used...."

Zyxwv99 (talk) 18:53, 25 November 2011 (UTC)

It is a matter of style and the Wikipedia Manual of Style advises against capitalisation except for proper nouns. It is also the convention in science not to capitalise unit names when spelled out, even when they are named after a person. On both count pound should not be capitalised. SpinningSpark 17:15, 26 November 2011 (UTC)

Then shouldn't somebody revert the edit of 15:54, 24 November 2011‎ by User:Jc3s5h? I'm still a novice and don't feel THAT bold. Zyxwv99 (talk) 16:03, 27 November 2011 (UTC)

Go for it! Gerardw (talk) 16:11, 27 November 2011 (UTC)

Just Do It! WikiDMc (talk) 00:32, 28 November 2011 (UTC)

Tower pound image

Conversion to shillings does not give user useful information in the context of a Pound (mass). If tower pound is notable because of it's use in currency, let's mention that in the paragraph. 02:36, 14 December 2011 (UTC) — Preceding unsigned comment added by Gerardw (talk • contribs)

I agree that Tower Pound is not the measure of 'mass'. But since the article mentioned the Tower Pound, and I had the picture of the prototype, thought of adding it up. Anyways, its influence on the currency system cannot be neglected. In fact I would urge you to include the fact of its influence on the currency system in the main paragraph too... I believe an article must be holistic, rather than being strict. ~ DebashisM (talk) 03:08, 14 December 2011 (UTC)

As far as I know, the Tower pound was never used on the currency side. In the Middle Ages, people had a strong sense of fairness that was often a bit illogical. They would not have accepted having to bring more pounds of bullion to the mint than they would have received in coins. The Tower pound appears to have been a solution to this problem. The bullion you brought to the mint was weighed in Tower pounds, and then you got the same number of pounds in coins. Because the Tower pound was significantly heavier than the sterling pound used for minting (I forgot if it was the troy pound at the time or something else), the difference was enough to account for the inevitable losses in the minting process and the operation of the mint and the operator's profit. This is why it was called the Tower pound: It was used only in the Tower, where the London mint was located at the time. (Source of the information: A relatively recent scholarly book called Weights and measures in Scotland.) Hans Adler 07:36, 14 December 2011 (UTC)

Hans, truly speaking I do not know of the accuracy of the details. The picture I uploaded is of the Tower Pound prototype that I had clicked during my visit to the Tower in May 2011. It is based on what I read on the placed placard (wish I had clicked it too) and what was told by the present ravenmaster, Chris Skifes.

The currency pound was divided into 240 shillings. The weight of these 240 shillings combined was equal to the weight of a 'Pound'

DebashisM (talk) 08:17, 14 December 2011 (UTC)

The book that I got the information from is relatively recent and contains ground-breaking new research (such as the Scottish inch actually not being slightly longer than the English inch, after all) that hasn't become popular knowledge yet.

Yes, the currency pound was of course divided in that way until February 1971. But I really think it's off-topic w.r.t. the Tower pound, which shouldn't get so much prominence in this article anyway, given that its role is not completely clarified yet. Hans Adler 08:29, 14 December 2011 (UTC)

I saw the tower pound written in the article, and I had a picture of the prototype - If you feel its off the topic, then go forward and delete the same. I have no qualms... ~ DebashisM (talk) 09:16, 14 December 2011 (UTC)

Well, I primarily see coins in that photo. I guess the oblong thing on the left-hand side is a tower pound standard or something? If it is, then the way it's arranged may give a misleading impression. I am not asking to remove the photo. It's quite decorative, but maybe we shouldn't accompany it with text that suggests more than that. Hans Adler 09:24, 14 December 2011 (UTC)

DebashisM, the picture is a great addition to the wall-of-text article, we just want to get the caption right. Hans, I've added a note based on your information above; could you complete the citation? Do you think we should splinter the Tower pound section into a (very small) article of its own? Gerardw (talk) 15:40, 14 December 2011 (UTC)

Sooner or later we should probably have a separate Tower pound article, but first I must buy the book. In Leeds I simply borrowed it from the library, but there doesn't seem to be a single copy in all of Vienna. I will order it in January.

Sorry, what I wrote here wasn't fit for article space. That's why I qualified everything with "if I remember correctly". And in fact, based on a Google Books search it appears that I misremembered something. [7]

I do have access to a relevant paper by the same authors as the Scotland book. [8] I find the following rather interesting (and it also contradicts something else I said above):

The English troy ounce is recognized as a weight unit in very early English coinage, but its formal use in metrological definition is much more recent. It was not yet an official bullion weight in England in Pegolotti’s time and its subsequent formal introduction seems to have occurred in the late fourteenth century.31 The commercial pressure for this change almost certainly came from the important markets of the Low Countries, and indeed the English troy ounce is the same size as the ounce of the Bruges silver mark. Before this time, the principal ounce used in England was the ounce of Cologne, one of the principal European bullion markets, whose mark had widespread application in north Germany and the Low Countries. In English metrology, the Cologne ounce is more familiar as the ‘tower ounce’—a name acquired from its use at the Mint, in the Tower of London, where it controlled coinage operations until 1527. It is sometimes thought to have been restricted to use in the Mint, but in fact it was the general ounce until eventually superseded by the troy ounce.32 Its identification as the Cologne ounce was confirmed by Pegolotti.33"

It appears that I swapped the function of the troy and Tower pounds in my mind. Sorry for that. More later. Hans Adler 17:33, 14 December 2011 (UTC)