[Dixielandjazz] RE: Slide trombones

Dan Augustine ds.augustine at mail.utexas.edu
Mon Mar 21 12:56:31 PST 2005

     Many thanks to Professor Edgerton's disquistion on the nature of 
cones and parabolas.  A fine job.  But it reminds me (as does just 
about everything) of Ambrose Bierce, who referred to cones in his 
definition of 'publish': "In literary affairs, to become the 
fundamental element in a cone of critics."  I hope Mr. Edgerton and i 
escape this fate in these publications.


P. S. Tubas are primarily conical (except in the valve-section 
tubing), so we tuba-players can move in on the skirt immediately 
without fear of success (except on St. Patrick's Day, when such 
skirts might conceal a disagreeable surprise).
>From: "Edgerton, Paul A" <paul.edgerton at eds.com>
>To: "'Dixieland Jazz'" <dixielandjazz at ml.islandnet.com>
>Subject: RE: [Dixielandjazz] Slide trombones
>Date: Mon, 21 Mar 2005 14:22:13 -0600
>Time for another DJML science lesson: today's word is "parabola."
>A parabola is a conic section. That is, one can take a cone standing on its
>circular base -- a trombone will do nicely -- and slice it parallel to the
>axis of the cone.  The resulting curve is called a parabola.  Anybody who
>has seen the Gateway Arch in St. Louis or watched a perfectly thrown "Hail
>Mary" pass has seen what I'm describing.  (Kids! If you try this experiment
>at home, use a sharp band saw -- but ask permission first!)
>The mathematically significant feature of a parabola is that it has a focal
>point.  In the case of a trombonist, the focal point is typically seated at
>the bar in a short skirt.
>When a parabola is rotated through space about its axis, it forms a
>paraboloid.  One common paraboloid is a satellite dish antenna. Another is
>the reflective surface of an old-style automotive headlamp.  If a trombonist
>is rotated about his axis, he gets dizzy.  The same effect is generated when
>he sits at the bar next to the skirt.
>The purpose of a horn is to couple an acoustic radiator with the focal
>point, so it isn't correct to say a brass instrument's bore is parabolic.
>Now that you have now been properly educated, you can avoid making
>embarrassing mistakes like this in conversation with the skirts at the bar.
>All brass instruments have bores that are conical, and most contain
>cylindrical sections to accommodate things like tuning slides.  The trumpet
>and trombone, in particular, have a bore that is predominantly cylindrical
>with the conical sections being mainly in the lead pipe and bell.
>Wait a minute, I have just received new information that the primary
>definition of the word "parabolic" is "Of or similar to a parable."
>Ahem, please forget I ever mentioned the skirt at the bar.
>-- Paul Edgerton

**  Dan Augustine     Austin, Texas     ds.augustine at mail.utexas.edu  **
**      "Most Texans think Hanukkah is some sort of duck call."       **
**                       -- Richard Lewis                             **

More information about the Dixielandjazz mailing list