Monday, 6 July 2009

Summer solstice bivvy on the summit of Schiehallion

As a summer solstice walk on the 21st June, Jim & I decided to climb Schiehallion with a view to bivvying on the summit, making a long exposure pinhole photograph on 5x4 film recording the duration of the night (there were around five hours of darkness). 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. There was an extremely strong cold wind blowing, so the cameras were supported by little piles of stones - camera cairns!

The wooden pinhole camera is in the bottom left hand corner of this image.

...and this was a cardboard camera which we nestled in amongst the summit cairn itself. The perspective and distortion of the image is rather misleading.

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, froze and left as soon as the dawn came.

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 deduced. 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 devised a graphical system to represent large volumes of surveyed heights, later known as contour lines, which we now all use on our OS maps.

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

Image made from the pinhole camera facing North

Image made from the pinhole camera facing South

We seem to be making a bit of a regular thing of walking at the pivotal points of the years cycles of light and dark.

No comments:

Post a Comment