Watching the rain at Lingholm

 We were having lunch in the greenhouse at Lingholm when it was pointed out that the clip on the centre of the glass produced a much wider and therefore clearer flow of water.

 The central drip started from part of the window opening mechanism much higher up. This ran down the centre of the pane.

Somehow the outside of the clip seemed to be bringing together narrow beads of rain and joining them to make wider sections. The narrower sections are more opaque because the curvature of the water is greater and so it has more of a lensing effect on the light by refraction. Lots of little sections of this close together acts like frosted glass. If the same water is spread more widely in a thinner layer, it refracts less and is easier to see through.