Wave flight over Scottish mountains

I wonder how many of you recognize this?

If you have ever been a glider pilot then you will know it’s a barograph trace recording the height the glider reached- in this case 15,000ft.

In my search for a Monomonday line challenge I found it amongst M’s collection of gliding memorabilia. (We both used to be glider pilots- that’s how we met).

In the old days you made a barograph trace by first smoking the paper and a needle recorded the changing pressure as the glider rose through the air currents, in this case wave over the Scottish mountains.

Today it’s all digital.

PS We used to fly from Portmoak airfield near Kinross. In those days it was £15 for a trial flight- now it's £85!