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Kieran Kelly says that A. C. Gregory, the Australian surveyor and explorer,
preferred a pannikin of black tea for his artificial horizon. I'd supposed the
tea might prevent a reflection from the bottom of the container, if that was
bright. Got to wondering if perhaps tea had a sheen that would make it show dim
objects better. So, just now, I set out two similar containers. One had
water, the other the same amount of strong black tea made with loose, rather than
tea bag, tea.

With the sun's reflection I couldn't tell if there was a difference in
brightness. What I did notice was that the tea seemed to settle more quickly after
being ruffled by a breeze. Switching the places of the two containers didn't
change the effect, so it wasn't that the tea was less exposed.

My quick experiment doesn't prove anything, and the effect, if there, was
modest. Perhaps others will examine the merits of tea more carefully. According
to Kelly, one of the reasons Gregory liked tea better than mercury was that he
could drink it after the observation.

Bruce

   

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