13 Ashley Place S. W. | Jan. 29. 1861
Dear Tyndall
I send for your examination1 (as you desire) a similar sheet to the one you had before.2 This sheet is advanced two stages beyond the preceding. It is marked in small figures with the lunar hour to which each observation most nearly belongs. (By these Lunar Tables have been formed) and 2d The “daily means omiting disturbances” are calculated. This enables me to collect the daily means into weekly means, of which there will be 52 in each year; always commencing with Jan[uar]y 1st—and throwing Feb. 29 (if there are 29 days in that month) and Dec. 31 with the mean of the nearest 7 days. —(Feb. 29 with the mean of the 1st March, and Dec 31 with that of Dec 27).
Having then a series of 52 weekly declinations in each year, I can investigate the mean amount of secular change <1 word illeg> 7 Declin, diminishing) the systematic regularity or irregularity of the secular change in aliquod parts of the year. The possible annual variation; season or otherwise—Systematic influences on the Declination of the Suns revolution on its axis, the Moon’s declination, her phases, &c. &c.
I shall very shortly have 3 years Kew Ob[servatio]n ready for this examination—and have 5 years at Hobarton3 of similar investigations ready.
I had a letter from Becher4 today from Giessen. He too is engaged in experiments on Radiant Heat.
Sincerely y[ou]rs | Edward Sabine
RI MS JT/1/S/21
RI MS JT/1/TYP/4/1316
I send for your examination: enclosure missing.
a similar sheet to the one you had before: see letter 1760. Following on from letter 1760, this letter describes the next stage in the work at Kew Observatory to create lunar tables from the data collected. The records of the positions were then entered into monthly lunar tables, according to the lunar hours each position corresponded to the most. From these the mean variation in each lunar hour in each year was calculated. Every hourly position which differed from the mean of the same hour in the same month was then regarded as evidence of the presence of a magnetic disturbance. See E. Sabine, ‘Results of the Magnetic Observations at the Kew Observatory. No. III’, Phil. Trans., 156 (1866), pp. 441–51 (on pp. 441–2).
Hobarton: The observatory in Tasmania.
Becher: possibly Dr Emil Becher (d. 1884), a German physician. He was appointed Acting Assistant-Surgeon in the Medical Services of the British Army in 1855, and promoted to staff surgeon in 1868. A paper by Becher was presented at the Royal Society of London on 26 February 1863, with Sabine as President in the Chair: E. Becher, ‘On the Effect of Temperature on the Secretion of Urea, as Observed on a Voyage to China, and at Hong Kong’, Roy. Soc. Proc., 12 (1863), pp. 440–1. In the paper Becher reported a series of observations during his voyage in China, including meteorological observations, on the relation between extreme variations of temperature and his bodily secretions of urine, urea, and sodium chloride during each day.
Please cite as “Tyndall1764,” in Ɛpsilon: The John Tyndall Collection accessed on