It’s almost Christmas. Let’s have a story about a man named Yule.

In the early nineteenth century – my period – and in the science of terrestrial magnetism – my subject – getting scientific instruments to work correctly and predictably on a consistent basis was both vital to the science and an extraordinarily difficult thing to achieve. One of the most enjoyable aspects of my research so far at the Royal Society has been encountering faulty terrestrial magnetic instruments. For these were fickle beasts; they baffled, perplexed, vexed and puzzled their users time and again.

The capability of any terrestrial magnetic instrument was reduced by environmental changes and the exigencies of travel, as well as the loss of strength that any magnetised needle is subject to over time. The problem was that magnetic instruments had to travel – often over great distances – to collect data from across the globe; for the earth’s magnetic field in its entirety could not be studied from one single place. Thus geomagnetic research in the early nineteenth century often presented as something of a paradox, travel being both essential and detrimental to the instruments of its making.


Travel case for a dip circle, used to measure the angle between the horizon and the Earth’s magnetic field, c.1830. Author’s photo taken in the stores of the Science Museum, London.


This peculiar problem was showcased in great detail in the autumn of 1840 at Aden (then a British settlement, now in Yemen), one of the many places chosen at this time to become a site for the erection of a geophysical observatory for the regular observation of terrestrial magnetism. The Aden observatory was to be part of the Magnetic Crusade (a posthumous title) which began in 1839 and aimed to establish and join up similar such observatories all over the globe. A geomagnetic project on this scale had never previously been attempted. One of the central tenets of this project – that which gave it unity and greatness – was that observations in all the distant observatories were made simultaneously, with the same methods and the same instruments. The centre of operations was Britain, from which place instruments were dispersed to the observatories.

The instruments in question here arrived in Aden, from Britain, on August 30, 1840. However, they were decidedly not the same instruments which had left Britain and which were supposed to help link all the observatories together.

Enter Yule. Sir Henry Yule is known to posterity as an eminent geographer and scholar of Central Asia, noted especially for his acclaimed two-volume work on the travels of Marco Polo, first published in 1871. In 1840, however, Yule was a Lieutenant in the Bengal Engineers experiencing his first taste of Asia. His initial assignment was the delivery of a set of magnetic and meteorological instruments to establish Aden as an observatory. The journey to Aden had taken Yule, and the delicate instruments, over the sea and across the desert.

On arrival at Aden, when Yule unboxed the instruments, it became immediately apparent that all was not well. Of the 55 magnetic and meteorological instruments and assorted scientific accessories sent from England, only 33 arrived in the same state in which they departed. With the aid of several abacuses I have managed to calculate this as a less-than-satisfactory 60% survival rate. However, only one of the several magnetic instruments and large magnetic bars arrived unscathed. They were rusted, damp, cracked, maladjusted or simply ‘broken’ by the time Yule set eyes on them. The instruments had not been packaged – or, to continue on our Christmas theme, wrapped – appropriately. Nor, like many a cheap toy opened on Christmas day, had the instruments been constructed appropriately, Yule alleged in a long list (which one assumes he checked twice) of the instruments’ conditions sent back to England in September 1840.


A dip circle, rather more expertly packed, in its travel case, c.1830. Author’s photo taken in the stores of the Science Museum, London.


In fact, the report on one particular instrument’s condition – the horizontal force magnetometer – reads not unlike a post-Christmas complaint letter sent to some shoddy manufacturer:

‘The Circular wooden frame works intended to inclose these two Instruments on being lifted out of the packing case fell to pieces. They appear to have been constructed in a manner unadapted to this climate being composed of small pieces of wood ingeniously built together but retained in their places only by a band of thin mahogany veneer. This having warped and split no other bond remained … in the boxes containing the smaller parts of the apparatus all the little bindings of wood intended to keep the Articles in place were found loose, having been attached by glue only, and the Articles in consequence adrift in the boxes.’

Yule was thoroughly unprepared for this eventuality. And, sadly for Yule, there was no one in Aden to whom he could turn for expert advice on what to do with the instrumental disarray to which he was now subjected. He had expected to find a more qualified officer – Lieutenant Western – in situ, but unbeknownst to Yule this man had ‘unfortunately died some months ago’. Though Yule had received tuition (and carried with him written instructions) in magnetic and meteorological instrument use, the situation was far beyond his skill, and he even alleged that there were instruments transmitted with him with which he ‘had no acquaintance whatever, and which were never alluded to.’



Description of the defects found in a second, vertical force magnetometer transported to Aden, from the ‘Proceedings of the Committee assembled … to inspect and report upon such magnetical Instruments as may be laid before them by Lieutenant Yule, Bengal Engineers’ (Royal Society MM/11/149)


Unsurprisingly, Aden never made it as a magnetic observatory, though it did eventually contribute important meteorological data. By this time, however, Yule was long gone, having obtained his leave very shortly after first arriving at Aden. Given the preceding, this is also unsurprising. He was roundly criticised by his superiors – Edward Sabine in particular – on receipt of his report, it being believed that ‘had there been a person on the spot competent to have directed the proceedings’, the instruments in their changed condition could have been managed and made to work at least reasonably well.

Though George Airy believed that given a few days training even idiots may observe very well, in 1836 it was contrarily remarked that good magnetic observation demanded from the observer an uncommon union of skill and experience. Such skill and experience was not just required in perfect conditions however, as the above demonstrates, but in a range of circumstances. And it did not just apply to observing the instruments, but in engaging with and managing their physical, mechanical, state in various degrees of disrepair. The unfortunate Yule did not seem to possess this level of expertise. The effect this might have had on his yuletide cheer is unknown.

Merry Christmas!


Matthew Goodman is a second year PhD candidate at the University of Glasgow working in collaboration with the Royal Society on the subject of terrestrial magnetism, scientific instruments, and science in expeditionary contexts in the nineteenth century.


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