OED and definition of "siphon"

victor steinbok aardvark66 at GMAIL.COM
Wed May 12 21:55:44 UTC 2010

The NODE definition is still wrong. Atmospheric pressure is not what
maintains the flow, although it is important that in a proper siphon
/of this type/ the containers are not sealed. When pressure is used in
the apparatus of this design, it is called a pump. When there is no
pressure, it is a siphon.

It is actually a key point that atmospheric pressure be nearly equal
in both containers. If the initial container is sealed and the
pressure drops as liquid is dispensed, the siphon action will
eventually cease, because the pressure on the terminal end will
counteract any forces that allow the flow to continue (including
gravity--which is why the terminal end is /lower/ than the initial
end). More specifically, action in a siphon is produced by
"hydrostatic pressure" combined with gravity (hence the need for the
/surface/ of the liquid in the terminal container to be /below/ the
/surface/ of the liquid in the initial container). The relative
lengths of the tubes are actually quite irrelevant, although the most
common type has one shorter and one longer end out of practical
considerations. You can actually have two equal-length tubes stuck
into two identical containers placed at the same level, as long as
there is more liquid in one than in the other. When the amounts even
out, the siphon action stops.

On the other hand, in the bottle siphon, it is the pressure
differential that causes the action. If you don't recall the normal
function of a siphon bottle, it is sealed nearly full with water, but
it is essential that some space is left filled with air--that is, the
water level should not be too high. Once the seal is engaged, a pump
or a gas cartridge discharge fills the air space with carbon dioxide.
Additional carbon dioxide is then dissolved in the water. When a
passage is opened by engaging the siphon bottle (usually a lever or,
sometimes, a button), the pressure differential forces the
liquid--along with dissolved CO2--out of the bottle. Other than both
being means of transmission of liquid from one container into another,
the two siphons have absolutely nothing in common.

Consider, for example, that in the late 1980s-early 1990s, an
apparatus similar to the siphon bottle was devised for spraying oil. I
believe, the original device was called Oil Mister and its descendants
are still available in kitchen gadget stores. That device was powered
by a hand-pump--before spraying, you pushed the top of the Mister up
and down, forcing air into the can, then released the aerosol button
to spray. Although the action was nearly identical to the siphon
bottle--aside from the additional effect of carbonating the water
which was not present in the Mister--I do not recall anyone ever
referring to it as a "siphon".

A couple of other points. The OED has a citation from Shaw under 1.c.

1898 G. B. SHAW Plays II. You never can tell 307 Waiter... Scotch and
syphon for you, sir?

This is interesting because it does not appear to refer to the
/bottle/, but rather to its /content/. In other words, what is mean by
the phrase is essentially "scotch and soda", except that the "soda"
comes from a siphon bottle. This does not match the definition for

    c. ellipt. A siphon-bottle, esp. one containing aerated water.

What is particularly ironic about this definition is that it carries
absolutely no meaning. How does one define "siphon" as a
"siphon-bottle" without knowing what a "siphon" is in this context?
The definition is cyclical. One is expected to know what a
siphon-bottle is before realizing that it can be abbreviated as just
"siphon". Let's just say that 1.a. is not the only definition that
needs work.

Then there is the zoological "siphon":

    3. Zool.    a. = SIPHUNCLE 1.
1822 J. PARKINSON Outl. Oryctol. 174 The partitions, siphon, &c., of
this fossil are those which are to be found in every species of
Belemnite. 1858 GEIKIE Hist. Boulder vi. 107 The inner tube that
traverses the centre of the chambers from end to end of the shell is
called the syphon.
    b. A tube-like organ serving as a canal for the passage of water
or other fluid; also, a breathing-tube or suctorial organ.
1826 Phil. Trans. 353 The Buccinum, when completely buried, is enabled
to communicate with the water by its respiratory syphon. 1840 Cuvier's
Anim. Kingd. 445 A sucker, or siphon,..occupies the place of the
mouth. 1872 H. A. NICHOLSON Palaeont. 217 The margins or lips of these
orifices are usually drawn out..into longer or shorter muscular
tubes,..termed the siphons. 1888 ROLLESTON & JACKSON Anim. Life 449
The mid-foot..forms two lobes which usually fuse together, and
constitute the siphon.
    c. (See quots.)
1888 ROLLESTON & JACKSON Anim. Life 561 In the Desmosticha and
Petalosticha a tubethe siphonarises from the posterior extremity of
the oesophagus and lies closely applied to the inner margin of the
intestine into which it opens again at or near the end of the inferior
coil. 1896 tr. Boas' Text Bk. Zool. 137 The so-called siphon, or
accessory intestine, is a very peculiar structure occurring in most

Let's just say that these definitions also were not written by
scientists. And the quotations actually point to obsolete biology.
Wiki has a rather extensive article on siphons in moluscs (see the
disambiguation under "siphon"). The future OED editor for this article
should take a close look at it.

Siphons carry different functions in gastropods (e.g., apple snails
and garden snails), cephalopods (cuttlefish and octopodes) and
burrowing bivalves (e.g., clams commonly known in New England as
"steamers" and geoduck). Cephalopods use it as an equivalent of a jet
engine. Some gastropods use it to spray water on internal gills or
sensory organs that detect food. Other gastropods send no liquid
through it at all and use it as a snorkel instead. Bivalves that have
it use it for multiple purposes--and siphons in geoducks can be up to
1 m long. And not all of these organs are actually related to each
other despite some morphological similarities and the use of the same
name. And this is just mollusks!! There are organs referred to as
"siphons" in other species.

The bottom line is that this article--along with a number of
others--may need to be farmed out not just to one specialist, but
several (finding someone skilled in both physics, morphology of
mollusks and botany is exceptionally hard these days). At the very
least, once written, it should be checked over by specialists before
it is released. Sadly, as has been pointed out, other dictionaries are
not much better at getting at the juicy details.


On Wed, May 12, 2010 at 12:10 PM, Robin Hamilton
<robin.hamilton2 at btinternet.com> wrote:
> _The New Oxford Dictionary of English_ (my copy to hand is the 1998
> printing), which is to a degree independent of the OED (it's not simply a
> Concise or Shorter version, but an independent text) makes a significant
> change from the definition found in the OED itself:
> _______________________________________
>  SIPHON:  a tube used to convey liquid upwards from a container and then
> down to a lower level by gravity.  Once the liquid has been forced into the
> tube, typically by suction, atmospheric pressure on the remainder in the
> container maintains the flow.
> _______________________________________
> ...

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