|
|
|
|
|||||
|
||||||
Subject: Re: Reaching the pole. (was Nautical Almanac)
From: Trevor J. Kenchington (Gadus@XXX.XXX)
Date: Thu Jul 04 2002 - 09:04:28 EDT
George Huxtable wrote:
> Amundsen took with him to Antarctica one Mercury horizon
> and two Norwegian glass ones, which presumably were used with sensitive
> spirit-levels with a strong alcohol filling to avoid freezing.
Pure ethanol freezes at -117 Celsius (again, according to CRC tables).
Given the difficulty of getting the last water out of any alcohol, a
real spirit level would likely freeze at a good bit higher temperature,
(though still well below the -40 at which a mercury artificial horizon
would become useless). I'm not sure that I would want my life depending
on the alcohol remaining fluid under Polar conditions.
Is it possible that the glass horizons used some form of suspended prism
or mirror, with no fluid component?
Trevor Kenchington
-- Trevor J. Kenchington PhD Gadus@XXX.XXX Gadus Associates, Office(902) 889-9250 R.R.#1, Musquodoboit Harbour, Fax (902) 889-9251 Nova Scotia B0J 2L0, CANADA Home (902) 889-3555Science Serving the Fisheries http://home.istar.ca/~gadus
|