|Spanish translation & annotations|
Berlin 1875 June 30
Berlin 1875 June 30
On the 1st day of June I left Hamburg and came to Berlin. I at once went to see His Excellency Herr General-Lieutenant Dr. Baeyer, the director of the Prussian Geodetical Institute. I found him a very courteous and interesting old gentleman with opinions of his own upon pendulums. He has come to the conclusion that he will not use the reversible pendulum and will endeavor to persuade his colleagues of the council of the European Gradmessung to give it up. He thinks invariable pendulums swung in vacuo are the thing; if one could only invent a vacuum apparatus. As General Baeyer has no place for my experiments, I arranged with Professor Förster, President of the German "Aichungs Commission" or Commission of Weights and measures to allow me to make them in that building. He gave
me my choice of several rooms, one of them a very remarkable place for performing experiments which require great uniformity of temperature. It has immensely thick walls the inner part of which is of hollow brick and the whole is lined with zinc chambers. In the middle is an immense brick pier which extends several metres underground. This room has no diurnal change of temperature and the yearly change is such that when there is a difference between the temperature of the room and that of the external air of 20º the temperature within changes at the rate of 0º.3 in twenty-four hours.
The reversible pendulum which as you remember was intended to be a copy of that of the Prussian Geodetical Institute used on the European Gradmessung is provided with a standard metre of peculiar construction with which to measure the length of the pendulum. What I desired to do and have now nearly completed was to compare the two standards of the Prussian Instrument and of ours. Having therefore made the arrangements mentioned above I went back to Hamburg and devised in conjunction with the Mssrs. Repsold a proper arrangement for supporting both standards at once on my stand.
The Mssrs. Repsold, most intelligent and I may say scientific gentlemen, were very prompt in making what I wanted but there was some delay in getting the Prussian standard as nobody seems to think a day is anything here. When I finally received it, I was about a week learning the peculiarities of the instruments, for it is quite clear to me that the Prussian standard has at some time received an injury although it shows no mark of any kind, and Dr. Bruhns on page 143 of his memoir in the publication of the Royal Prussian Geodetical Institute for 1870 refers to an indication of something of the sort but he does no mention what I found namely that when the standard was made vertical according to the level which accompanies it, the upper scale is not vertically over the under one. In short, I believe the instrument has been bent. In consequence of this discovery I wish to insure our instrument against the effects of a similar accident and I have therefore arranged with Dr. Förster to compare a brass line metre which I have ordered of Repsold with the German Normal Metre next winter and again early in the following summer. I might make the comparisons this sum-
mer but I am unwilling to have a metre bar cast and then use it at once without allowing it some months to attain a complete recovery from the cooling process.
Both the standards belonging to the pendulums are provided with metal thermometers which work beautifully but as the standards are used in a vertical position the weight of the metal thermometer presses on the standard when one end is up & shortens it. Consequently I compare the standards in 4 positions, viz.:
-Prussian thermometer scale up. U. S. ditto. up
" " " " " " " down
" " " down " " " "
" " " " " " " up
My comparisons are not yet all made but I will inclose a table of those I have made with this letter. They agree very well and show that our standard is about 0mm.133 longer than the Prussian and as Förster has found that the Prussian is 0.m999860 parts of the German Normal Metre, it follows that ours measures 0.m999993 parts of the same Normal Metre.
Immediately in arriving here I wrote to Liverpool to have my pendulum apparatus forwarded but after vexatious neglect it has just come. If I find it in first rate order I shall set it up at once. Otherwise I shall wait till it is put in order or until I can have the new apparatus.
I have opened my chronograph and found it injured. I sent it to Bond before I left America to be put in good repair & to be carefully packed to come abroad. But on opening it I found one of the 2 large screws that clamp the clock-work down onto the large iron bed of the whole loose and the other dropped out. The consequence was that the end of the clock worked had bunged back and forth and broken about a dozen different pieces. These screws could not possibly have been tightened before the apparatus left Bond’s & they should pay for its repair.
I must again call your attention to the fact that I have not yet informed how my vouchers are made out and consequently can render no accounts whatever. I do not learn that any deposits have been made with my bankers and I seem to be conducting operations at present at my private expense.
Yours very respectfully
C. S. Peirce
P. S. The following are the comparisons I have made so far between the two standards. The final redaction have not yet been made; no investigations of micrometer screws etc. having been made.
When both scales are supporting their own weight U. S. Standard is longer by more 0.131 (¿?)
Compression of Prussian scale when supporting weight of metallic thermometer 0.001
Compression of U. S scale when supporting weight of metallic thermometer 0.0030
Comparisons, neither supporting thermometers.
U.S –Pruss. 0.1312
_________ another of 1297 accidentally omitted from calculation
Comparisons, both supporting thermometers
Comparisons, Prussian only supporting thermometer
Comparisons, U. S. only supporting thermometer
The microscopes magnify about 30 times, so that without very careful pointing better work could hardly be done. But I have no doubt better can be done if I can protect the standard better from radiation. But this is quite ¿? the errors of the determinations of seconds pendulums which are not less than 0.0030 (mm).
Transcription by Max Fisch (Peirce Edition Project), revised by Sara Barrena
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Proyecto de investigación "Charles S. Peirce en Europa (1875-76): comunidad científica y correspondencia" (MCI: FFI2011-24340)
Fecha del documento: 17 de septiembre 2012
Última actualización: 10 de mayo 2016