A Virtual Slide Rule

I don't usually get all excited about virtual slide rules, but this one really got my attention. Worth a visit to see it.

John B Jervis

John Bloomfield Jervis

While I was posting on the  redevelopment of the High Bridge last week, I thought it might be appropriate to do a post on John B. Jervis, the chief engineer for the Croton Aqueduct.  I started poking around on material that I could readily find on him and found two good sources.  The first was at the Rome NY library, which not only houses his archives, but also was bequeathed to the City of Rome along with an endowment by John B. himself. The following biographical information is presented from the Rome Library website with permission:

John B. Jervis (1795-1885) was America's leading consulting engineer of the antebellum era (1820 - 1860). Jervis was a pioneer in the development of canals and railroads for the expanding United States. He designed and supervised the construction of five of America's earliest railroads, was chief engineer of three major canal projects, designed the first locomotive to run in America, designed and built the forty-one mile Croton Aqueduct (New York City's water supply for fifty years: 1842 - 1891), and the Boston Aqueduct. Jervis authored a book on economics, The Question of Labor and Capital (1877); helped found a local industry, the Rome Iron Mills; and, of course, is the founder of Rome's public library.
Jervis bequeathed his home and personal library to the city of Rome, New York, to be used as a public library. His personal library is kept intact as a memorial and for research purposes. The papers of John Jervis number in the thousands, and include memoirs, manuscripts of books he authored, scrapbooks, folios and quartos, nearly 600 engineering plans and drawings (some in watercolor), maps, public documents, and countless letters and reports. His library also includes 1,800 monograph volumes on general topics as well as a concentration on applied sciences and civil engineering. Copyrights and dates of publication range from the 1670's through the 1880's.
Jervis began his career in Rome as an Axeman for an Erie Canal survey party in 1817. By 1823 he was superintendent of a fifty-mile section of the Erie Canal. In 1827 he was appointed Chief Engineer of the Delaware and Hudson Canal project. It was John Jervis who suggested that a railroad be incorporated into this project. At this time there were no railroads in America, but Jervis won approval of his idea and even designed the railroad's locomotive, the Stourbridge Lion, the first locomotive to run in America. In honor of his work on the Delaware and Hudson, Port Jervis, N.Y., is named for him.
In 1830, as Chief Engineer of the Mohawk & Hudson Railway (the first section of what was later to be the N.Y. Central R. R.), Jervis designed "The Experiment." This was the first locomotive in the world to have a free-swinging, four-wheel front truck, which gave the vehicle greater maneuverability and enabled it to travel at an unprecedented speed of eighty miles per hour. The Jervis design became the standard American design.
The monumental task of building New York City's forty-one mile water-supply system (The Croton Aqueduct) was given to Jervis in 1836. The system included the Croton Dam, the Ossining Bridge, the Harlem River Bridge, the Receiving, Equalizing, and Distributing Reservoirs on Manhattan, as well as the magnificent embankments, tunnels, and arches employed throughout the aqueduct system. (Original illustrations and engravings of these structures are preserved in the Smithsonian Institution and in the Library of Congress). The six-year project employed over 4,000 workers, and when completed, carried seventy-five million gallons daily to New York City.
Jervis's other notable contributions include the design and construction of the following: the ninety-eight mile Chenango Canal (1833), the enlargement of the eastern division of the Erie Canal (1834), the Boston water supply project (1846), the Hudson River R. R. (1847-1850), the Michigan Southern & Northern Indiana R.R., the Chicago & Rock Island R.R. (1850 - 1858), and he was general Superintendent of the Pittsburgh, Fort Wayne & Chicago Railway (1861-64). Again, we must stress that these undertakings were "pioneering" ventures. Jervis's projects were filled with "first" and "untried" engineering principles, and as such, were "schools" for a generation of American civil engineers.
Jervis returned home to Rome in 1864. In 1869 he organized the Merchants Iron Mill, which survives today as the Rome Iron Mill. He spent the remainder of his life writing and in 1877 published a book on economics, The Question of Labor and Capital. Upon his death he bequeathed a large portion of his estate to the city of Rome for a library. His personal library remains as a special collection in Rome's Jervis Library. A Library of Congress representative noted that it is one of the most complete sets of early railroad and canal reports and maps in existence.

                                                 ^v^v^v^v^v^v^v^v^v^

I note here that while it is not clear from the material above, John B. Jervis was a self educated man. He did not attend any institution of higher education. According to Lori Chien of the Rome Library,

"He apprenticed with Benjamin Wright on the Erie Canal and learned on the job, and also read widely on his own.  You may be interested in reading these two books about his life:  "The Reminiscences of John B. Jervis, Engineer of the Old  Croton," and "John B. Jervis:  An American Engineering Pioneer" by F. Daniel Larkin. ... Please note that the Jervis papers are open to qualified researchers by appointment only, which needs to be made at least two weeks in advance."

Like many other Enlightened individual of that era like Joseph Priestley, whom I have written about extensively, John Jervis demonstrated that a formal education was not necessarily a requirement for significant scientific and technological contributions. I think that these individuals can teach us much about the human mind and how profound understanding of knowledge can be acquired.

I also note that while Jervis was clearly on the leading edge of Civil Engineering for his day, I find no evidence that he and Edwin Thacher had ever communicated with each other.

I once had the occasion to travel to Ossining NY to buy some specialized paint from a manufacturing facility right across the street from the SingSing Prison (Ossining Correctional Facility).  While there I decided to explore the prison since it was so famous and so many movies made reference to it. I went to the gate and asked the guard if there were tours.  He told me to get lost, but that if I was interested in the prison there was always the Ossining Museum, which had an exhibit on the prison.   I went to the museum and was delighted with the exhibit on the prison and also the exhibit on the Old Croton Aqueduct and John B Jervis. I highly recommend a visit there if you are in the area for both of the exhibits.

Also, since the High Bridge Aqueduct is now being reconstructed, you might find this site of interest:

The High Bridge and Tower in New York City

On January 11, 2013, Mayor Michael Bloomberg broke ground for the $61 Million redevelopment project on the High Bridge,  New York's oldest bridge spanning the Harlem River onto Manhattan island.  The project is expected to be completed in the summer of 2014.  The High Bridge was part of the Croton Aquaduct System which I wrote about a few days ago.

The High Bridge is now a steel arch bridge, with a height of almost 140 feet over the Harlem River. The eastern end is located in The Bronx, and the western end is located at Highbridge Park, in a section of Manhattan island called Washington Heights.

Although High Bridge has been closed to all traffic since the 1970s, it remains the oldest surviving bridge in New York City although, in fact, most of the current bridge dates from only 1928.

Interior staircase of the High Bridge Water Tower

Originally designed as a stone arch bridge, the High Bridge had the appearance of a Roman aqueduct. Construction on the bridge was started in 1837, and completed in 1848 as part of the Croton Aqueduct, which carried water from the Croton River to supply the  city of New York some 10 miles to the south.  High Bridge has a length of well over 2,000 feet. It was designed by the aqueduct's engineering team, led by John B. Jervis. 

High Bridge with Original Pillars (as seen in 1890) viewed from the Bronx toward Manhattan.
The High Bridge Tower can be made out in the distance near the terminus point of the bridge.

The Croton Aqueduct had to cross the Harlem River at some point, and the method was a major design decision. A tunnel under the river was considered, but tunneling technology was in its infancy at the time, and the uncertainty of pursuing this option led to its rejection. Don't forget the problems with building the casons for the Brooklyn Bridge decades later further south on the East River.   A low High Bridge  would have been simpler, faster, and cheaper to construct. When concerns were raised to the New York Legislature that a low bridge would obstruct passage along the Harlem River to the Hudson River, a high bridge was ultimately chosen.

In 1928, in order to improve navigation in the Harlem River, all of the masonry arches of the central part of the bridge that spanned the river were demolished and replaced with a single steel arch of about 450 feet. Of the masonry arches of the original 1848 bridge, only one survives on the Manhattan side, while ten survive on the Bronx side.

Officials were thinking of closing the bridge in the mid 1960s due to disrepair, then in 1970 a pedestrian threw a rock from the bridge onto a tour boat, and the bridge was closed.  On January 11, 2013 the mayor's office announced the bridge would reopen for pedestrian traffic by 2014. 

Three Harlem River bridges: High Bridge (showing the steel arch that replaced the original masonry spans), nearest; Alexander Hamilton Bridge (part of I-95); and the Washington Bridge, farthest. Washington Heights is left and the Bronx on right)

From the Bronx

The High Bridge was part of the first reliable and plentiful water supply system in New York City. As the City was devastated by cholera (1832) and the Great Fire in 1835, the inadequacy of the water system of wells-and-cisterns became apparent. Numerous corrective measures were examined. In the final analysis only the Croton River, located in northern Westchester County was found to be sufficient in quantity and quality to serve the needs of the City. The delivery system was begun in 1837, and was completed in 1848.

The Old Croton Aqueduct was the first of its kind ever constructed in the United States. The innovative system used a gravity feed, dropping 13 inches  per mile and running 41 miles into New York City through an enclosed masonry structure crossing ridges, valleys, and rivers. University Avenue in The Bronx was later built over the southernmost mainland portion of the aqueduct, leading to the bridge. The High Bridge soars 138 feet above the 620-foot wide Harlem River, with a total length of 1,450 feet. The bridge was designed with a pedestrian walkway atop the Aqueduct and was not used for vehicular traffic. Though the carrying capacity was enlarged in 1861-62 with a larger tube, the bridge, obsolete due to opening of the New Croton Aqueduct, ceased to carry water in 1917. In the 1920s the bridge's masonry arches were declared a hazard to ship navigation by the United States Army Corps of Engineers, and the City considered demolishing the entire structure. Local organizations called to preserve the historic bridge, and in 1927 five of the original arches across the river were replaced by a single steel span, the remaining arches were retained.

Exploring How the Mind Acquires Information

I ran across the following tidbits:

I met George Fuller.  He worked for his father in a
a furniture factory.  George was trying to sell me the
the sofa that was made in their factory.

and,

Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae.  The rset can be a total mses and you can sitll raed it wouthit a porbelm.  Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.


Do you have any other examples to show how the mind works a little differntly than you might have originally thought?

If you did not notice in the first paragraph above, please note the repetition of the words at the end of each line and the beginning of the next line. Most people will read this without noticing.

I am dyslexic. I have trouble distinguishing between certain letters. For example, "p" and "b" are very confusing for me, as in "pig" and "big".  Or, between "b" and "d" like in "big" and "dig". It is interesting that I don't confuse "pig" and "dig". I have confused "dog" and "god".  What is surprising to me above with the paragraph about the research at Cambridge University is that I have no trouble reading that paragraph, so why do I have trouble with the words I cited above? I will have to do some research on this point.

Since I am dyslexic, I cannot read very fast.  I think the best I can do is about 100 words a minute.  
I describe it this way.  It takes me a little extra effort to get the information from the page into my brain, but, once I get it in there, I do not have any problem processing it.

I have auditory dyslexia also,  This means that when someone tells me their phone number, I cannot process that information fast enough to get it into my brain. Consequently, I cannot repeat it. It is lost - forever.  Perhaps this is why, when it comes to mathematics, I have no difficulty whatsoever manipulating complex mathematical formulas in my head -- once I have assimilated the formula, that is.

I think that I have a better feel for symmetry than most people. I think it is because of the symmetric dyslexia.  You know "p" and "b" and the like.

I would be very interested to hear from others who suffer from dyslexia. I have not spent much time dwelling on this in my life. I have not discussed it much with others.  The only consequence that has impacted me is that when I was very young I did have difficulty reading and I was left back from 3rd grade to 2nd grade and I didn't perform well when reading any quantity of text was involved.
My way out was through mathematics.  I seemed to have no difficulty with it whatsoever.  

Huell Howser - Noted California Explorer

Photo provided by Howser Production Company

It is with great sadness that this blog reports the passing of Huell Howser (October 18, 1945 – January 7, 2013).  Huell, most noted for his explorations and ramblings through California, became famous recording the geography, culture, and history of the Golden State in his PBS TV show "California's Gold" from 1994 through 2012. Huell was a unique character who was a native of Gallatin, Tennessee who thrived in his adopted state of California with his love of everything Californian.

For more information on Huell Howser please see his Wikipedia entry.

Farewell fellow traveller and discoverer. We will miss you.

New Developments on the Croton Aqueduct

Courtesy Library of Congress
High Bridge Aquaduct circa 1900 as seen from University Ave in the Bronx
looking toward Manhattan and the High Bridge Tower

An engineering marvel of its time, the Old Croton Aqueduct was a water delivery and distribution system constructed for New York City between 1837 and 1842.  It was a gravity fed system 41 miles in length from the Croton River in Westchester County to the reservoirs and water distribution systems on the island of Manhattan in New York City.  Significant components of this original system are still in place and in use today, approaching 200 years later.

Today, with Mayor Michael Bloomberg on hand, New York City broke ground on a $61 million project for the restoration of the High Bridge, a non functioning aquaduct bridge that spans the Harlem River.  High Bridge is the oldest remaining bridge in New York City and while it stopped carrying water to Manhattan as part of the Croton Aquaduct system in 1917, it was closed for public use around 1970 for pedestrians and cyclists from the Highbridge section of the Bronx to the Washington Heights section of Manhattan.  The new development project, when completed, will reopen the bridge to pedestrians and cyclists and is expected to be completed in 2014.

I lived immediately adjacent to the High Bridge Aquaduct and the accompanying Tower that was used as a vent to allow the water to go down into the water system back in the 1940s.  It was a different era then.

The history of the Croton Aquaduct is very interesting.  An aquaduct was necessitated in the early 19th century because the existing water supply for the city had become polluted and inadequate for the need of the city.   Manhattan had a very limited supply of fresh water available since it is completely surrounded by brackish rivers.  Before the aqueduct was constructed, residents of New York City obtained water from cisterns, wells, natural springs, and other bodies of water. 

The unsanitary conditions that arose before the existence of the aquaduct caused an increase in disease. Epidemics ravaged the city as a result of the polluted aquifer, overcrowded housing, the lack of sewers, public ignorance of basic sanitary conditions, and the existence of polluting industries near wells and residential areas. These conditions contributed to an unprecedented mortality rate of 2.6% in 1830. In addition, the rapid expansion in densely packed wooden buildings, combined with a lack of an adequate water supply, led to many fires, culminating in the 1835 Great Fire of New York, which destroyed large parts of the city.

The need for a new supply of fresh water was crucial and in 1837 construction began on a massive engineering project. supervised by Chief Engineer John B. Jervis, to divert it from sources upstate. The Croton River was dammed, aqueducts were built, tunnels dug, piping laid and reservoirs created. Iron piping encased in brick masonry was laid from the Croton Dam in northern Westchester County to the Harlem River, where it continued over the High Bridge at 173rd Street and down the west side of Manhattan and finally into a Receiving Reservoir located between 79th and86th streets and Sixth and Seventh Avenues that is now the site of the Great Lawn and Turtle pond in Central Park.  The Receiving Reservoir was rectangular tank within fortress-like rusticated retaining walls, 1,826 feet by  836 feet; it held up to 180,000,000 gallons of water. 35,000,000 gallons flowed into it daily from northern Westchester.

From the Receiving Reservoir water flowed down to the Distributing Reservoir, better known simply as the Croton Reservoir, a similar fortification located on Fifth Avenue between 40th Street and 42nd Street, where the main branch of the New York Public Library and Bryant Park are located today. This reservoir was built to resemble ancient Egyptian architecture. 

The Aqueduct opened to public use with great fanfare on October 14, 1842. The day-long celebration culminated in a fountain of water that spouted to a height of fifty feet from the beautifully decorated cast-iron Croton Fountain in City Hall Park. Among those present were then-President of the United States John Tyler, former presidents John Quincy Adams and Martin van Buren, and Governor of New York William H. Seward.  

Water started flowing through the aqueduct on June 22, 1842, taking 22 hours for gravity to take the water the 41 miles to reach Manhattan.  Even though only 6,175 houses had been connected to the system by 1844, the Croton water had already dramatically improved both domestic hygiene and interior design. Baths and running water were being built in the private homes of wealthy New Yorkers and public bathing facilities were created for the masses. The water system had another inadvertent consequence. The decline in the number of residents drawing water from the city's wells resulted in a rise in the water table which flooded many cellars. To address this problem, the city built sewers in many residential streets. By 1852, 148 miles of sewers had already been constructed.

Despite its size, the capacity of the Old Croton Aqueduct could not keep up with the growth of New York City, and construction on a New Croton Aqueduct began in 1885 a few miles east. The new aqueduct, buried much deeper than the old one, went into service in 1890, with three times the capacity of the Old Croton Aqueduct. It currently supplies ten percent of New York City's water. The Croton Receiving Reservoir continued to supply New York City with drinking water until 1940, when Commissioner of Parks and Recreation Robert Moses ordered it drained and filled to create the Great Lawn in Central Park. The old aqueduct remained in service until 1955; in 1987 the most northern portion was re-opened to provide water to Ossining.

New Dimensions in Slide Rule Technology

The other day I posted that there is a new record that has been set with the development of the Eximius Diu 6 slide rule by David Hoyer. Please see my post on this subject.

In thinking about this slide rule I realized that it is a member of a class of slide rules that doesn't get much attention.  Let me be more specific.
We are all familiar with the linear slide rule.  This is a slide rule like the K&E Deci-Lon. Here the scales are linear and can be moved relative to each other with the aid of a cursor to keep track of specific points on the scales and to transfer a reading from one scale to another.
Also, we are all familiar with the circular slide rule. This would be slide rules like the Gilson Midget Circular Slide rule. Here there are typically two indicators that you can set the distance between and then move them to another position on the slide rule without changing the angle between them.
Finally, there are the cylindrical slide rules Like the K&E 4012 Thacher slide rule.  Here, in effect, the scales are wound in a helical fashion around a cylinder.  This was done to get a longer scale in a smaller space, increasing accuracy. Interestingly, Prefessor Fuller and his cylindrical slide rule call his slide rule "spiral"

What David Hoyer has done with his Eximius Diu 6 slide rule design is to put a spiral scale on a flat surface, somewhat like a circular slide rule, but, unlike the circular slide rule, there is more than one revolution (or turn) that the scale transverses.  Another way of looking at this is that the circular slide rule is the degenerate case of the spiral slide rule where the scale only traverses one revolution.

The way to use the spiral slide rule is very similar to the circular slide rule with two indicators to mark the difference indicating an angle between two numbers.  But, unlike the circular slide rule where there is no ambiguity as to where the resultant number (solution of the multiplication or division) is located, this is not the case with the spiral slide rule.
Specifically, there are multiple possible results where the indicator crosses a scale and the user must select one.  The only way to determine which of these crossings is the correct one as suggested by Hoyer is to use a more conventional slide rule, either linear or circular, to approximate the solution, and then find the place where the indicator crosses the scale "near" the approximation. While some might say that this is begging the question of why use the spiral slide rule, the answer, of course, is accuracy.  The Eximius Diu 6 pulls in a full 6 places of accuracy over its entire scale.

But, there is something unkosher about using this method to find the solution to an arithmetic computation on any slide rule. If you are going to use another device to get the solution, you may as well use an electronic calculator in the first place and get a precision of much greater than 6 places of accuracy.

So, the question I pose is whether there is some sort of mechanism in the way of arms, etc. that would allow the Eximius Diu 6 the throne for which it is intended?   Can we construct it in such a fashion that we do not have to go out to some auxiliary device to pull the answer out of the hat, so to speak?

Please comment below if you have a solution to this problem.

Analog Clocks: My Generation’s Slide Rule by Sue Frantz

This post is a reprint with permission from Technology for Academics
It is by Sue Frantz and it is entitled "Analog Clocks: My Generation's Slide Rule" and first appeared 1/31/12. I might add that I did not include either analog clocks or slide rules in my list of historic milestones in human civilization in an earlier post.

ANALOG CLOCKS: MY GENERATION'S SLIDE RULE

A couple weeks ago I was sitting in our psychology lab when a student wandered in.

Me: Can I help you?

Student: <locating the clock on the wall> I was wondering what time it is.

The student is visually impaired, judging by how close he was standing to the clock and how he was squinting.

Me: It’s 20 ’til 11.

Student: What?

Thinking the student is also partially deaf, I speak up.

Me: IT’S 20 ‘TIL 11.

Student looks at the clock, clearly baffled. Another student in the lab chimes in.

Student #2: It’s 10:40.

Student: Oh! I’m late!

Finally it dawns on me. The student didn’t know how to read an analog clock. He wasn’t a young student, either; probably in his thirties. I mentioned this to a colleague who has a teenage daughter. He said that she also can’t read an analog clock. Although he wasn’t entirely convinced she could tell time at all judging by her inability to be on time. There are some confounding variables there, granted.

One week later I’m back in the lab when another student wanders in; this one is younger. I’m thinking, “Here we go again.”

Me: Can I help you?

Student: <locating the clock on the wall> I just wanted to know what time it is.

Student stares at the clock.

Student: <wanting to give it a try> It’s 9… no, it’s 10… 10…

Me: 10:40.

Student continues to stare at the clock not quite believing me.

Me: It’s actually 10:37.

Satisfied, the student walks out.

[Side note: Weirdly, both of these events did take place at 10:40-ish.]

Now I’m not curmudgeonly enough to say that everyone should know how to read an analog clock. In our digital world, it doesn’t matter. Slide rules were very useful right up until calculators became small enough and cheap enough for most everyone to have. It’s been years since I had an analog watch, or a watch of any kind for that matter; the digital display on my cell phone works just fine when I’m on the go. When I’m in my office, my computer provides a nice digital readout in the bottom right corner.

A few colleagues and I were discussing this phenomenon recently. One person wondered what that was going to do to the concepts of clockwise and counterclockwise. Will the terms disappear or will they continue to be used but with their origin largely forgotten, like “the whole nine yards”? Apparently it’s becoming something of an issue because I noticed the recent addition of helpful arrow icons to Adobe Reader. Maybe in the end it will just be “rotate right” and “rotate left”.

Another colleague wondered what will happen to “the top of the hour.” That one may hang on with its origins eventually lost, but I’d say that the days are numbered for “quarter past” and “quarter ’til”. “Half past” may also be doomed.

If you’re feeling adventurous, show your students a few images of an analog clock and ask them to write down what time the clock is showing. I’d be curious to hear how many can do it. Post your results in the comments below.

Demonstration Slide Rules

The other day, when I wrote about the retro steampunk slide rule table  that was advertised on the internet.  I mentioned then that I have three such slide rules myself (not tables, but slide rules).  I had occasion to be talking to the son of an associate of mine from 40 years ago.  I had seen a note that he had constructed, at that time, the world's largest slide rule.  I then proceeded to tell him about my three demonstrators.

In doing so, I found myself recounting how I had stumbled onto them and thought it might make a good post.

The first demonstration slide rule I acquired was the K&E Deci-Lon (68-1100) and here is how I acquired it.

Back in 1997 I was interested in buying some books and eBay seemed to be a good source for them, sometimes. If I found a book on eBay I would check out the availability of the same book  on Bookfinder.com.  Sometimes Bookfinder was cheaper, sometimes more expensive. I would use that as my guide as to whether to bid or not on eBay.

I noticed that there were some books for which I had no interest that seemed to be selling for rather steep prices when compared to the prices listed on Bookfinder.  One particular book of poetry sold for about $150 on eBay and there were over a dozen copies on Bookfinder ranging around $10.  I ordered a copy on Bookfinder.  When it arrived I was surprized to see how tiny a book it was.  Anyway, I listed it on eBay.  The bidding was fierce and it sold for about $120.  I then bought another copy of the book on Bookfinder and again listed it on eBay.  A repeat of the previous auction and the book sold for just $115.

I then went back to Bookfinder and bought half a dozen copies of the same book.  I listed the book for the third time on eBay and, again, it sold for a substantial price over $100.  But, this time, after the auction ended I got a phone call from some fellow down in Texas who wanted to bid on the book and was at some football game during the last hours of the auction (back in those days it was still possible to contact the seller by phone). He said, "Please tell me that you did not sell that book to someone else." He went on to explain why he did not bid on the book and that he very much wanted it.
I told him that I just happened to have another copy of the book and I would be glad to sell it to him for the same price that the book had just sold for on eBay.  He seemed to be an interesting enough fellow, and we talked more.  In the conversation it came out that I collected slide rules.  He said to me that he had this slide rule, a demonstrator slide rule, that he had and would I be interested in swapping the book for the slide rule.  We agreed, and he shipped the K&E Deci-Lon 68-1100 to me in exchange for the book.  The book of poetry had cost me about $10 and the shipping was another few dollars.  So, I was very happen when my big and beautiful Deci-Lon arrived in perfect condition (and he paid the freight!)
I have used this slide rule as a valence over the window in my office for years.

The next demonstration slide rule I obtained was the Pickett 1010-ES.

This slide rule was part of a collection of about 200 slide rules that I bought near Oakland CA.  The fellow who had collected the slide rules had died and his daughter wanted to sell the collection.  I'll never forget that day when we were driving down the highway in a convertable with the top down with the slide rule hanging out there like a surf board.  I got more than a few looks on that trip.

The last demonstration slide rule is the K&E Polyphase 4053. I found this one on Craigslist up in the Seattle area. I had it shipped down.

I enjoy having these slide rules placed around the house and would entertain buying a few more.