Author Archives: Trilce Sandoval Similä, Curatorial team research student

Polar exploration

In my previous post I mentioned Sir John Franklin’s doomed expedition to the Canadian Arctic, on which the HM ships Erebus and Terror tragically disappeared with all 129 men on board after the summer of 1845.

While we wait and see what Canada’s renewed rescue efforts might discover about Franklin’s last journey, I think there are some items from his more successful voyages in the Science Museum’s stores that deserve a closer look.

Variation compass and magnetometer, by Henry Barrow & Co. (Adrian Whicher / Science Museum)

One such object is a variation compass and magnetometer, which would have helped determine a true course in relation to the magnetic and geographic norths (which do not coincide, as you may know), as well as measuring the intensity of the earth’s magnetic forces at different points at sea. Apparently used by Franklin on some of his Arctic voyages, it was later also used by others looking for the man among the ice! 

To complete my imaginary trek from pole to pole, I also found a Robinson dip circle taken to the other extreme of the globe by Sir James Clark Ross, on board HMS Terror, of all vessels.

A dip circle by Robinson, c.1830. (Alison Boyle / Science Museum)

After a string of successful expeditions up north, Ross set off on a magnetic survey mission to circumnavigate Antarctica between 1839 and 1843.

The magnetic needle of the dip circle, resting on the pivot at the centre of its case, would align itself to the Earth’s magnetic field, so the angle it made with the horizontal plane could be read off the graduated frame – this was of particular interest in polar regions, where the downward pull is the greatest, and where navigation with other instruments proved more difficult.

And to think that all this mileage is now under one roof…

Northward Ho!

I’ve been rummaging through the Science Museum’s collections looking for objects related to terrestrial magnetism and scientific expeditions.

I smiled when I came across the musical scores for “Northward Ho! or Baffled not Beaten” in a popular song catalogue from 1875 - it really brought home just how much Arctic exploration captured people’s imaginations in the second half of the nineteenth century.

Sheet music cover of "Northward Ho!" (Alison Boyle / Science Museum)

Commander John P. Cheyne of the Royal Navy, who penned the words for this dashing tune, was himself an Arctic officer. He took part in several voyages to the north, including Sir James Clark Ross’s 1848-9 search for Sir John Franklin’s lost expedition of 1845.

Franklin had been searching for the North-West Passage, when he and his crew suddenly vanished. Over the next fifteen years or so several expeditions were launched to find the missing hero, but only a few ominous clues about the men’s fate were ever found.

Sir John Franklin, 1824. (Science Museum / Science & Society)

Still, to Cheyne and others Franklin’s name would stand next to those of other revered explorers like Sir John Ross (James Clark Ross’s uncle*, as it happens) and Sir William Parry.

Lyrics from 'Northward Ho!" (Alison Boyle / Science Museum)

The cover print of the song shows three hot-air balloons, Enterprise, Resolute, and Discovery, preparing for flight in the Arctic. Balloons had been proposed as a method of reaching the North Pole as early as the 1870s as they could avoid some of the hardships and dangers of a journey by sledge or on foot, and could also provide useful platforms for making scientific measurements at higher altitudes.

Expeditions may have been a question of sport and glory, but they were also intended to gather accurate scientific data on a large number of natural phenomena, including the Earth’s magnetic field. Investigating terrestrial magnetism made a lot of sense in the nineteenth century, since the required equipment could improve the efficiency of navigation across the oceans.

'Proposed Method of Reaching the North Pole by Balloons', c 1880s. (Science Museum / Science & Society)

Some brave explorers, like Franklin, didn’t make it back from the unchartered northern territories. But the lucky ones returned with the magnetic instruments that had made their voyages possible. Many of them are now in the Museum’s store rooms. More about these soon…

*[Edited on 15/09/10]

Joule’s spiders

Before my first visit to the Science Museum’s stores, I’d imagined having to search for my mysterious magnetic instruments in the midst of much dust and cobwebs in the warehouse from the closing scenes of Citizen Kane.

In the rather more ordered and hermetically sealed rooms of Blythe House, the spider threads I found were of a much cosier sort. Encased in their own tiny frame, they rather reminded me of my great-grandparents in their wedding portrait.

Two kinds of Diadema spider thread, as used in Joule's dip circle. (Alison Boyle / Science Museum)

The two cocoons of Diadema spider silk are surviving samples of the types used in the dip circle designed by James Prescott Joule. (Yes, that Joule.)

James Prescott Joule, English physicist, 1882. (Science Museum / Science & Society)

As scientists became more interested in magnetic phenomena in the late eighteenth century, more effort was made to improve the apparatus used in their study. The friction of pivoted needles found in many magnetic instruments was a problem limiting the accuracy and ease of making measurements.

The usual method involved the needle’s cylindrical axle rolling on agate planes as it aligned itself with the surrounding magnetic field.

A needle on an agate plane, in a dip circle by Robinson, c.1830. (Science Museum / Science & Society)

Joule turned to spider threads to create an alternative suspension method. JD Chorlton examined one of Joule’s dip circles after the latter’s death, describing it as follows:

“The needle, constructed of a thin ribbon of annealed steel, weighing 20 grains, is furnished with an axis made of a wire of standard gold. This axis is supported by thread of the Diadema Spider attached to the arms of a balance suspended by a fine stretched wire. The whole is hung by a wire which can be twisted at the head through 180°”.

Strong, resilient and light, spider silk sounds like an ideal material. In practise the silk was too fiddly, and the needle’s weight and friction with the axle meant that the thread would be prone to snap. Still - it’s a lovely story which gives a sense of the patience, precision and ingenuity required of scientific investigation.