Cornhill Magazine,  7 (1863), 381–89.

A Night at Greenwich Observatory

[Alfred W Drayson]




Observatories, Instruments, Observation, Mathematics, Measurement, Astronomy, Instrument-makers, Electricity, Telegraphy, Psychology, Railways, Amateurism

    Describes the Royal Observatory at Greenwich as 'a certain edifice in which the longest calculations, the deepest thought, and the minutest care, are in operation day and night'. Accordingly, it is important that the signs on the building's doors read 'no visitors are admitted', as inside the 'instruments are most delicate' and for 'long calculations, perfect quiet is also necessary, and it is not improbable that the visitation of an occasional organ-grinder near the Observatory might lead to the wreck of some half-dozen ships, which had erroneously calculated their positions by data influenced for ill in consequence of the computer's nerves being tormented'. The author, 'anxious to acquire knowledge of the system adopted here', has nevertheless gained rare access to the interior of the Observatory. (381) He observes that the 'aim of all the time and labour' expended inside the building is 'to give accurately the position of the various heavenly bodies, and, from past and present observations, to be enabled to foretell for two, three, or four years in advance, the exact position of the sun, moon, and stars, at any instant during the twenty-four hours'. He notes that 'Upon the information thus afforded depends the accuracy of all large surveys in various parts of the world'. Many of these calculations are made using 'the large "transit-instrument"', a huge telescope, which takes up most of the 'principal observing room' and is 'the most important thing in the establishment'. (382) The usefulness of this 'great gun telescope', however, is dependent upon weather conditions, and a 'densely cloudy or foggy night is holiday time at the Observatory' (383). Another room contains several hundred chronometers 'all passing an examination, in order to test their regularity', and 'for a small sum, any maker may have his instrument tested at Greenwich'. Every one of the many observers employed at Greenwich 'has about his eyes an individuality which causes him to invariably perceive a phenomenon, such as the transit of a star, a little before or a little after another observer', and this 'personal equation' is 'a singular phenomenon well worthy of the inquiry of psychologists; for it would appear as though there was a variation in the rate at which the external senses telegraphed to the seat of reason' (386). According to the 'astronomical clock, indicating sidereal time' (387) the length of each day is 'not an uniform quantity of time'. But to have 'a variable length of day [...] in the present days of railway travelling regulating clocks would be a very difficult matter'. Therefore, 'For business, as well as scientific purposes [...] a day of uniform length is adopted, and this day is the mean of all the variable days throughout the year, and is hence called a mean day, and portions thereof "mean time"'. (388) The Royal Greenwich Observatory is 'a sort of head-quarters for all practical astronomical information' where the 'whole training and work of the various members partake entirely of the practical and mechanical'. However, it is not from there 'that any important discoveries connected with the nature and constitution of the various celestial bodies are likely to emanate'. Rather, 'From independent observers it is most probable that the next great advance will originate'. (389)

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