4 eigenh. Briefe mit U.
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Collection of four long, unpublished letters spanning more than a decade, all to the Berlin physicist and geologist Georg Adolf Erman (1806-77), who had returned from a long voyage around the world and was in the process of publishing his findings ("Reise um die Welt durch Nordasien und die beiden Oceane", 5 vols. of history [1833-42] and 2 vols. of physics [1835-41, with atlas]). Gauss was able to draw on Erman's empirical observations about earth's magnetic field. All four letters begin with thanks for gifts sent by Erman, then develop into extensive scientific discussions which even touch upon Gauss's thermogalvanic experiments. Also, Gauss mentions his attempts to obtain books of Russian fiction. - In 1836 Gauss thanks Erman for presenting him with the 2nd part of his "Reise um die Erde" ("Ortsbestimmungen und Declinationsbeobachtungen auf dem festen Lande"): "This work contains a great wealth of facts. I am particularly interested in your magnetic observations and therefore am glad that you decided to include in this early volume your compass declinations with their results. These, in connection with other observations, will serve to supply the gap left by Barlow's map of declinations [...] But now I dearly look forward to the publication of the second part which is to contain the intensities and inclination readings. Hopefully we will then soon possess a general map for the horizontal intensity, which is devoutly to be wished. Indeed, as things stand now, the entire intensity in most cases is to be conceived merely as a unit of calculation at which one cannot directly arrive with any degree of precision, but which is a mere function of immediately observable elements, such as one rarely will find together in a single place, and even more rarely with the same degree of reliability; and, even more importantly, there are precious few occasions on which the entire intensity will be of any use at all; what is really needed are those very separate elements themselves. To arrange the three coordinates in such a fashion that one of them represents the whole intensity would seem to me, considering the present state of affairs, like wanting to draw up a star index in longitude and latitude only, omitting right ascension and declination. Indeed, at close examination even this comparison proves misleading, as an astronomer ultimately needs latitudes and longitudes for planets and comets so as to establish a general theory, whereas to establish a general theory of the geomagnetic field deserving of the name it is indispensable to disassemble the whole intensity back into its components. To be sure, this statement, which you must not take as an off-handed remark but rather as the result of long and thorough deliberation, cannot possibly be explained in a letter, but this much I can add: that I am fully satisfied as to the method by which the establishment of an exhausting General Theory is to be attacked [...] You may be interested to learn that our recent thermogalvanic experiments have already succeeded in so amplifying an electric current that it is capable of setting even the 25 pound rods in violent motion after passing through a wire of a mile's length [...]". - In 1839 Gauss thanks for a "postcard from Kamchatka" and for the "full communication of Erman's declination readings": "I will be most happy soon to receive also the corrected data of your intensities, although there is no hurry about that. I am merely making mention of a few of your observations in an article intended for the 3rd part of the Findings of the Magnetic Society, the first sheet of which is now in the press. Should your corrected calculations for these 16 locations [followed by a table of 16 cities, including St Petersburg, Kazan, Moscow, San Francisco, and Rio de Janeiro] have yielded intensity readings departing from those published by Major Sabine, I would be able to include these changes in the proofs of the said article [...] According to the most recent news I received from England, our hopes that the government there might do something splendid for the study of the geomagnetic field have suffered a severe blow; but this is not for want of the scholars' diligence, and no blame can be attached to them if the government fails to act [...]". - In late 1841 Gauss thanks for the gift of the 2nd volume of "Reise um die Erde" ("Inclinationen und Intensitäten, Declinationsbeobachtungen auf der See. Periodische Declinationsveränderungen"): "Regarding your observations I can only agree with Sabine's judgment that they contain the most substantial and valuable contribution to the knowledge of magnetism ever made by anybody. It gives me pleasure to see that the new reduction of intensity readings for Tahiti differs considerably from the earlier one, approaching that of Fitz Roy, and nearly duplicating that of Belcher. The large difference, according to Sabine, is mainly due to local interferences [...] I am much pleased with your plans for a journal aiming at acquainting us with Russia's literary productions, the more so because I myself during the past year or two have begun to study the Russian language and find this occupation most agreeable entertainment. The only thing that rather spoils this hobby for me is the difficulty in obtaining Russian books [...] However, l'Appetit vient en mangeant, and in particular I should like to have more in the way of belles lettres. My fiction department so far is limited to Krylov's Fables, a few volumes of Pushkin, and the complete collection of the writings of your Yakutian friend Bestuyev-Martinsky. All my endeavors to obtain something through the German booksellers have been in vain; a single shop did not refuse me outright, but demanded, apart from other onerous conditions (such as that one must accept the shipment regardless of when it arrives, and whatever the charge), the absolutely precise titles of the books ordered [...]". - In 1849 Gauss thanks Erman for sending him various works, including the "3rd volume of the historical section of your travel account", and criticises an article that appeared in the "Report of the British Association for the Advancement of Science": "Observations all made from points upon or near a single line encircling the earth are quite as hopeless for such a purpose as would be the attempt to determine all the lunar elements and equations from the observations of a single week, even if they were made continuously from a hundred observatories. One might go even further and say that, to a degree, the observation data must not only encompass most of the earth's surface, but must also be more or less evenly distributed across the same [...] Altogether, the correction of my constants will certainly prove a tough nut to crack (for posterity), one that will turn out to be harder than the teeth of many a coming scientist [...]". - Clean and well-preserved throughout. Three letters are written in neat Latin handwriting, while that of 1841 is in German script, written somewhat overly carefully at first, then becoming more and more fluent and finally descending into a rather loose style.