|Spanish translation and annotations|
London 1875 April 30C. P. Patterson Esq.
Superintendent U. S. Coast Survey
Washington D. C.
In accordance with your instructions, I have to report upon the progress of my work during the month of April. I sailed from New York on the 3rd and after a comfortable voyage reached Liverpool on the 13th. Mr. Farquhar was affected disagreeably by the sea and as soon as we reached Queenstown he became worse and a few days after landing was taken down with a sharp attack of jaundice. He has now got rid of that but is still weak and quite unable to do any work. I think another week will set him right. I have included his surgeon’s bill in my vouchers and I trust it will be allowed. If not I think it would be fair to increase his pay a little as I believe his attack was entirely owing to his voyage. He did one day’s duty in Liverpool on the 13th and since has done nothing but carry a chro
|nometer etc. and go out to Kew with me to see the station and transit there.
I find that the Kew observatory has been made the base or as I should prefer to call it the origin for the pendulum experiments of the British surveys. The observations of Sabine and I think also earlier ones were conducted in a private house in London which is no longer available. Besides, there are several reasons why London is unsuited for such work. The Greenwich observatory is as you know on a very small piece of ground and there is no room there for a permanent pendulum building. Accordingly a special building for the purpose was erected at Kew and Captain Kater’s invariable convertible pendulum has been swung there. The pendulums used on the Great Indian Survey have been twice swung there, a year being allowed for the work on each occasion. A pendulum used on the Russian survey similar I believe to the one Repsold is making for me has also been swung there. At present, they are swinging a pendulum which is to be used on an Arctic expedition. In consequence of this it will be impossible for me to swing there for about a month, but at the end of that time the director promises that there shall be no difficulty.
Repsold promises me my new instrument in three weeks. Under these circumstances, I shall after obtaining much important information in this country proceed to Germany and not swing in England until next winter or spring.
I have had an interesting interview with Professor James Clark Maxwell who is a pendulum-swinger and a writer upon the mathematical theory of the resistance of the atmosphere and upon other subjects connected with Attraction. He is to make a pendulum having five knife-edges. The idea is perhaps a good one.
I find much to my surprize that they all swing their pendulums in vacuo; -that is to say at Kew, in India and in Cambridge at Professor Maxwell’s new laboratory.
I have still to see several distinguished gentlemen connected with pendulums, especially Professor Stokes who has investigated the resistance of the Atmosphere and who was largely consulted in regard to the methods of making pendulum experiments now used in the British work, General Sir Edward Sabine whom you know as a great swinger of pendulums, and Sir George Airy who swung at the top & bottom of a mine. I have visited the Greenwich observatory but the Astronomer Royal was away that day.
I feel the immense advantage of talking with all these
people. For example, in all I ever saw in relation to the effect of the resistance of the atmosphere on pendulums, it has been assumed that the resistance was proportional to the density of the air while the temperature has been left out of account altogether, but from considering the matter in the light of the mechanical theory of heat I was led to believe that the largest term of the resistance was independent of the density and also of the surface of resistance and was proportional to the absolute temperature. I was happy to find that Professor Maxwell who is one of the greatest authorities on the viscosity of air, and the best experimenter upon it, entirely agreed with me in this view.
Professor Maxwell was the man whom on the whole I most desired to see. I enjoyed my visit to him exceedingly. The Duke of Devonshire, -to whose family I believe the great Cavendish belonged- and who is himself the chancellor of the University of Cambridge, has given Maxwell a most splendid new physical laboratory which is just finished. The building itself is very roomy and built in the most solid manner. All the partitions are of brick. It is filled with the most admirable contrivances for performing all sorts of physical experiments in the best way & is supplied with magnificent and admirably planned apparatus.
I found there very much which interested me most deeply besides what related to my pendulum work.
I have as yet visited no instrument makers except Casella and Browning, both of whom are clever but nothing great. I have ordered a metallic manometer at Casella which he promises me shall be very good. It is to cost about 2 guineas.
I have seen two forms of mercurial barometer which have interested me. The first consists of two small tubes of different calibres welded together and the upper one sealed at the end, as in the figure. A column of mercury in this compound tube will be lengthened if it rises and shortened if it falls in consequence of the difference of calibre of the two tubes. Then if the length of the column is greater than what the pressure of the air will support the mercury will fall; but as it falls it shortens in length until equilibrium is established; and viceversa. In this way an increase of the length of the column of an inch is indicated by a rise of the mercury through 5 or 10 inches and so it is very easy to read the barometer. But the instrument is not susceptible of a high degree of precision as all depends on the calibration of the tube.
The other form of barometer consists of a short tube about a foot long open at the end and at the other end reaching into a large tube which is sealed about it as in the figure. This tube is set in a brass case like an ordinary barometer case with a vernier and with a fiducial edge which comes somewhere about the height of E. Onto this brass one screws at the moment of using it a cistern of mercury like an ordinary barometer cistern but closed at the top with a stopcock to keep the mercury in. This being screwed on the stopcock is opened & by the screw at the bottom the mercury is made to rise to the point E in the outer tube. Then the height in the inner tube shows the barometric height. The instrument I saw could only be read to hundredths of an inch but nothing prevents its being made even longer than an ordinary barometer and I am not at all sure that it would not be a better instrument. I am of opinion that there would be less sticking of the mercury to the sides of the glass because the mercury does not stick till the tube is heated to remove the air etc. which however must be done with the ordinary barometer. At any rate I do not see why this form of instrument has not great advantages over the aneroid. I can see only three sources of error in the use of it. 1st the atmospheric
|pressure may change between the time of screwing up the mercury & that of reading the height of the column. 2nd Owing to a tilt the capacity of the outer tube at the moment when communication with the inner one is cut off may vary. 3rd the outer tube may be elastic.
I regret that I have not more to report but the amount of personal business on my hands on first landing has prevented my doing more. But I have no doubt that before circumstances will admit of my swinging my pendulums all the work that can be done before that will be done.
My passport was received and is very welcome. The minister kindly permits me the use of the diplomatic mail bag.
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: 15 de mayo 2012
Última actualización: 14 de septiembre 2017