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Re: Slocum's lunars
From: Herbert Prinz
Date: 2003 Dec 13, 11:11 -0500
From: Herbert Prinz
Date: 2003 Dec 13, 11:11 -0500
Jan Kalivoda wrote: > The explanation of the expression "the greatest science" as a guess of the > longitude from crossing the border of two distinct currents off the coast > (or a guess of the effects of the stream and the wind effects for DR in > general) seems to be exaggerated by Frank. It is undoubtely the great > navigational skill and "art", but a sort of science? Maybe, Slocum had > understood this word in this sense, but I doubt. I don't consider this unlikely at all. The terms "ars" or "art", "Kunst", etc. have been commonly used in books that were of a nature that we would nowadays call "scientific". Conversely, as the word "science" came into a wider use during the 19th century (parallel with the profession of "scientist"), it was only natural to use it for _all_ the contents that was formerly described in those "art"-books. In other words, for Slocum "art" and "science" were synonyms. > Slocum's mention about the error in logarithmic tables cannot be explained > as a hint at his own error, which he sought to hide by pretext of erroneous > tables. Such tricks are common for beginners that failed the resolve the > task, but Slocum wasn't a beginner and he resolved his task of these unique > clearly attested lunars very precisely after all near Nukuhiva (if he isn't > a liar in your eyes). Not necessarily the trick of a beginner, but maybe a repression of his embarrassment; the reaction of somebody who should know better, but who's skill got rusty. Most puzzling about this is that he resolved the problem so easily. How on earth could he correct a faulty table of logarithms out there alone and without resources? First he re-took the observation. This was very reasonable. But next he went straight to the tables to look for a discrepancy. I would have verified my computation first. Either he was so confident in his that he did not see a need to check it; or he could not check it beyond repeating every step, because he might just have mechanically followed a procedure without really understanding its particulars. However, let's give him the benefit of the doubt and assume that he just does not tell us in his narrative about this important step. Searching for "a discrepancy in the tables, [he] found it. In the tables [he] found that the column of figures from which [he] had got an important logarithm was in error." Not an individual logarithm was in error (which could have been corrected easily by interpolation from adjacent values), but a whole column. Now, he does not say that he bypassed the erroneous table entries (for instance, by choosing an alternative reduction method, or by consulting an other set of tables), but he claims to have corrected the faulty ones. That's quite a feat! Likely, we are talking about reduction tables and not the almanac, because Slocum says "tables". The only logarithm in the almanac is the proportional log. of the difference of the distance. Funny thing, we have never heard about Slocum contributing corrections to published tables. I do not want to make an argumentum ex silentio as has been done before in this discussion, but I think that some research into contemporary tables could be beneficial here. Maybe one pops up that has a whole column of wrong logarithms. In the mean time, the assumption that Slocum misunderstood a table heading, an instruction, or some such thing, picked first the wrong column, and afterwards the correct one seems like a good working hypothesis to me. Herbert Prinz