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    Re: Life on the Ocean
    From: Frank Reed
    Date: 2019 Jan 14, 14:48 -0800

    Tony wrote:
    "I always thought those VERY EXPENSIVE instruments and tools were kept with great care"

    The evidence seems to contradict the hypothesis. One possibility is that the hypothesis isn't quite right. Another possibility is that the evidene isn't entirely valid. 

    Were those wooden quadrants (octants) expensive? Somewhat. Brand new, they certainly weren't cheap. But were they "very" expensive? That's probably inaccurate. They were widely available and produced in large numbers. Part of the problem here is that we often see beautiful specimens of instruments in fine cases in museum collections. They look expensive. But there's a huge sampling effect at play here that may mislead. Fine examples that have been perfectly preserved tend to make it into museum collections. Not many museums bother with collecting examples of objects in average condition. A new quadrant in perfect condition in a deluxe case was expensive. An average quadrant in a simple, utilitarian case was much less expensive. There are also "used" instruments, which make up a big portion of any market. In the era, quadrants were probably much less expensive than you imagine.

    For an analogy, thinnk of those wooden quadrants as the "plastic sextants" of their day. In 1836, around when this painting was created, quadrants were used for common sights ...latitude at noon, and sights for the local time (time sights) at other times of day. A navigator might also splurge for a metal sextant, but only if he intended to get longitude by lunars.

    Is a painting like this valid "primary source" evidence? To some extent, it certainly is. The painting was made in the period, and the artist was aiming for near-photographic, realist representation. It's what he "sees", which is not quite the same as what "exists". The painting has been staged, designed to look harmonious and clean, and the artist perhaps makes the scene more interesting by showing the instruments out of their cases and on-display. There is always some disconect from reality. How great is it? Without a time machine, we can never be sure.

    This may be a good place to mention again that "there are no theorems in history". Most of us, in the NavList community, interested in navigation first learned about analyzing the world from math and science and engineering studies. And we learned simple rules of logic, for example, that a single counter-example disproves any mathematical theorem. But history doesn't work that way, and principlles of formal logic can work against us. We can speak about trends and general qualities and developments in history, but there are always exceptions. Focusing on the exceptions misses the point. In mathematical logic, a single exception has fundamental importance. In historical analysis, a single exception may be nothing more than a curiosity.

    Frank Reed

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