91av

I work as a wildlife tour guide in the Scottish Highlands so I travel widely in remote corners of the northern Highlands and islands. On two occasions in late 2009 I have come across a pile of odd objects (see photos) scattered on the ground. The first time was on a remote island in Orkney; the second was a few weeks later at an altitude of around 900 metres in the Cairngorm mountains. Had they been near a road or habitation I would probably have dismissed them as just some sort of household electronic debris, but in both cases they were miles from anywhere. The pile I found in the was at least a 2-hour walk from any road, track or building. They appear to have a burnt and pitted charcoal-like solid centre encased in a hard, plastic-like cover. The ones in the Cairngorms also had some small, charred battery-like cylinders with them. Can anybody suggest what they are, and why they ended up in such unexpected locations?

• The debris is from an old weather balloon. I used to see these on the Scottish mountains all the time in the 1970s. A sharp eye would spot a silver mark lying on the heather where it had landed. As a child I walked miles with my dad to collect these for proper disposal.

If your reader found charred remains this was most likely on a managed grouse moor where one had landed in very long heather and could not be seen. The managers of the moor then burned the heather in rotation to improve the red grouse habitat. Such practise provides young heather for food and leaves long heather for shelter. The weather balloon would have burned in the fire, leaving hard parts such as the battery segments shown in the photos.

Pete Oswald, Taftshurie, Orkney, UK