MDDM18: That Great Tube

Sun Jan 27 05:59:15 CST 2002

   "'Ask you something, Sir?...What thought have you
given to getting that great Tube in the Door?'
   "'Oh, Mr. Bird calculated the whole thing, years
ago, over in England.  All on Paper.'
   "'Before there was ever a Scantling cut?'
   "'Before there was ever a Screw cut for the
Instrument.'" (M&D, Ch. 30, p. 297)

   "'Aye? and that great Telescope Tube thing ever
pointing straight up?  Heh, heh.  Why's it got to be
that big?'" (ibid.)

Main Entry: scant¡¤ling 
Pronunciation: 'skant-li[ng], -l&n
Function: noun
Etymology: alteration of Middle English scantilon,
literally, mason's [!] or carpenter's gauge, from Old
North French escantillon
Date: 1555
1 a : the dimensions of timber and stone used in
building b : the dimensions of a frame or strake used
in shipbuilding
2 : a small quantity, amount, or proportion : MODICUM
3 : a small piece of lumber (as an upright piece in
house framing)

http://m-w.com/cgi-bin/dictionary

>From  Silvio Bedini, "The Transit in the Tower:
English Astronomical Instruments in Colonial America,"
Annals of Science 54 (1997): pp. 161-96 ...

   "When Penn finally decided to invest in a zenith
sector, he commissioned the instrument-maker John Bird
to produce it.  Bird, who had become the mechanical
coadjutator of the Astronomer Royal, the Revd James
Bradley, was recognized in the sceintific world as one
of the eighteenth century's foremost English makers of
precision instruments." (p. 171)

   "The sector Bird made for Penn was the first
example of the instrument to incorporate improvements
previously suggested by the Astronomer Royal Nevil
Mskelyne.  These consisted of a modification of the
manner of suspending the plumb-line that corrected a
situation which had introduced an error of many second
per angle." (p. 172)

>From Edwin Danson, Drawing the Line (New York: John
Wiley & Sons, 2001), Ch. 6, "Mr. Bird's Contrivances,"
pp. 60-70 ...

"In May 1762, Thomas Penn wrote to [William] Alexander
[surveyor general of New Jersey] to say he had
received advive that an instrument called a zenith
sector would solve the latitude problem and that 'I
have bespoke one of Bird...'" (p. 61)

   "In his discussions with Bird, Penn was accompanied
by his advisers, including Nevil Maskelyne, who had
made recommendations for improving the instrument.... 
When completed, Bird's zenith sector, with its
micrometer tangent screw that read to a freaction of a
second of arc, was examined by [Cecilius] Calvert
[brother of 5th Lord Baltimore], Thomas Penn, and Dr.
Bevis [heh heh], who all proclaimed its excellence
despite the cost's being three times that of Sisson's
old instrument.
   "Among their shopping list of instruments, the
proprietors also reuired an astronomical transit
instrument.  It was suggested that Dr. Bevis's
equatorial telescope ... would be most suitable.  The
proprietors met to examine the instrument, but were
disappointed with what they found....  Fortunately,
Thomas Penn had commissioned another instrument in
addition to the six-foot-radius zenith sector.  This
was 'a transit and equal altitude' instrument ...; it
would prove to be second only in practical value
during the North American survey to Bird's very fine
zenith sector." (pp. 63-4)

   "The most precise of the astronomical instruments
acquired by the proprietors for the North American
campaignb was John Bird's six-foot-radius zenith
sector.  This instrument consited of a tall stand,
probably eight feet high, frohm the top of which was
suspended from a pivot a six-foot-long telescope tube.
 At the base of the stand was fastened the
instrument's engraved ivory scale, which was a sector
with a radius of six feet--hence the name." (p. 65)

Sector (Page: 1301)
Sec"tor (?), n. [L., properly, a cutter, fr. secare,
sectum, to cut: cf. F. secteur. See Section.] 

[...]

3. An astronomical instrument, the limb of which
embraces a small portion only of a circle, used for
measuring differences of declination too great for the
compass of a micrometer. When it is used for measuring
zenith distances of stars, it is called a zenith
sector. Dip sector, an instrument used for measuring
the dip of the horizon. -- Sector of a sphere, ¡Å
Spherical sector, the solid generated by the
revolution of the sector of a circle about one of its
radii, or, more rarely, about any straight line drawn
in the plane of the sector through its vertex. 

http://machaut.uchicago.edu/cgi-bin/WEBSTER.sh?WORD=Sector

Zenith (Page: 1678)
Ze"nith (?; 277), n. [OE. senyth, OF. cenith, F.
z¨¦nith, Sp. zenit, cenit, abbrev. fr. Ar. samt-urras
way of the head, vertical place; samt way, path + al
the + ras head. Cf. Azimuth.] 

[...]

3. -- Zenith telescope (Geodesy), a telescope
specially designed for determining the latitude by
means of any two stars which pass the meridian about
the same time, and at nearly equal distances from the
zenith, but on opposite sides of it. It turns both on
a vertical and a horizontal axis, is provided with a
graduated vertical semicircle, and a level for setting
it to a given zenith distance, and with a micrometer
for measuring the difference of the zenith distances
of the two stars. 

http://machaut.uchicago.edu/cgi-bin/WEBSTER.sh?WORD=zenith

John Graham's Zenith Sector, at any rate  ...

http://atschool.eduweb.co.uk/bookman/library/ROG/P77.JPG

And back to Danson, Drawing the Line.  Ch. 8, "The
Southernmost Point of the City," pp. 79-92 ...

   "A week after arriving in Philadelphia, the
precious scientific instruments were brought ashore
from the Falmouth packet.  There were logistical
preparations to attend to; contracting carpenetrs,
organizing supplies, buying winter clothing, and
fitting out their field operations room in the
Statehouse.  It was not until Friday, November 25,
that the zenith sector was carefully unpacked and
inspected for damage after its long sea voayge from
England.  The following Monday the transit instrument
was checked.  Both were found to have survived
undamaged." (p. 83)

"Friday and Saturday were taken up with more meetings,
discussions, and examination of instruments.  John
Bird's beautiful zenith sector was insepcted minutely,
while Mason extoled its virtues; such an exquisitely
accurate instrument had never been seen on American
soil.  Bird's 'transit and equal altitude instrument'
was compared with Dr. Bevis's so-called transit
telescope.  The two English surveyors condemned the
latter out of hand as totally inappropraite for the
task, preferring the more portable, less complex, and
far more precise Bird transit." (pp. 83-4)

And see as well ...

Daumas, Maurice.  Scientific Instruments
   of the Seventeenth and Eighteenth Centuries.
   Trans. and ed. Mary Holbrook.  New York:
   Praeger, 1972 [1953].  [Ch. 2, "Surveying and
   Astronomical Instruments," pp. 173-87]

Hellmann, C. Doris.  "John Bird (1709-1776):
   Mathematical Instrument-Maker in the Strand."
   Isis 17 (1932): 127-53.

Turner, Gerard L'E.  Scientific Instruments 1500-
   1900: An Introduction.  Berkeley: U of California
   P, 1998 [1980].  ["Sectors," pp. 83-5.]

http://waste.org/mail/?list=pynchon-l&month=0109&msg=59889&sort=date

All right, closing in here ...

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