Schiehallion

pinhole photograph recording the hours of darkness on the mountain’s summit on the shortest night. Collaborative work made with Jim Hamlyn.

Silver Gelatin Print 2009-12 12.2x10.2com (5x4 contact print)

Text from Mountains Without End

Bivouac on the Summit of Schiehallion

As a summer solstice walk, Jim and I decided to climb Schiehallion with a view to bivouacking on the summit, making a long exposure pinhole on 5x4 film recording the 5 hour duration of the night. We set off and got to the top around 10pm just as the light was beginning to fade, but still having plenty of time to set up “camp" on the only sheltered area of the boulder field, and figure out where to make the images. In the end, we opted to have one camera point roughly towards north, and another in a southerly direction. A strong cold wind was blowing, so the cameras were supported by little piles of stones - camera cairns!

We’d rather assumed we’d have the summit to ourselves, but clearly others had also thought of walking on the solstice too, so at 1am were awoken by two walkers passing close by along the ridge. They found a spot maybe 50m away from us, but in the cold wind, and without sleeping bags, left before dawn.

Schiehallion’s isolated position and regular shape led it to be selected by Charles Mason for a ground-breaking experiment to estimate the mass of the earth in 1774. The deflection of a pendulum by the mass of the mountain provided an estimate of the mean density of the earth, from which its mass and a value for Newton’s Gravitational Constant G could be deducted. Mason turned down a commission to carry out the work and it was instead coordinated by Astronomer Royal Nevil Maskelyne. He was assisted in the task by mathematician Charles Hutton, who thus devised a graphical system to represent large volumes of surveyed heights, later known as contour lines, now universally used in mapping.

Ours was another act of measurement, but in this instance, of light and duration.