I saw this in a movie from the 1920s, set in the USA. ("Safety Last".)

At the top of a tall building, there are two strange objects which I believe I've seen before but never could figure out what they are for:

  1. A metallic (?) arrow, possibly meant to show which direction the wind currently has. But how can the arrow know which direction is "forward"? And who would actually need this visual information, only seen from afar, by others?

  2. A kind of cross with little balls in the ends. I believe it was spinning around semi-slowly. I truly have no clue whatsoever what this one might be for.

enter image description here

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    $\begingroup$ The arrow's tail with a larger surface area would be blown away from the wind and point to the direction the wind is coming from. Likely stationary, the cross structure could be a lightening rod. Neither of these may be functional and might have been made by the props department. I don't know if these were added to buildings of that time frame. Just thoughts. $\endgroup$
    – Jim Clark
    Commented Nov 20, 2021 at 18:52
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    $\begingroup$ the arrow is a weather vane $\endgroup$
    – jsotola
    Commented Nov 20, 2021 at 19:51
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    $\begingroup$ The 4 balls look a bit like an anemometer for wind speed ; but it does not look like it can spin as would be needed. $\endgroup$ Commented Nov 20, 2021 at 20:05
  • $\begingroup$ @blacksmith37 OP did say 'I believe it was spinning around semi-slowly'. $\endgroup$ Commented Nov 20, 2021 at 20:51
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    $\begingroup$ And IMDB's "goofs" list for the film includes 'The anemometer's rotation at the top of the building between cuts suddenly goes from spinning to standing still [and back again]' and 'The prop anemometer at the top of the building is composed of spheres, instead of the half-spheres of a true anemometer.' $\endgroup$ Commented Nov 20, 2021 at 21:08

1 Answer 1


Both are wind measuring devices usually placed at the highest point of a building.

The one with the arrow is called a wind vane, weathervane, or weathercock, as sometimes a chicken replaces the arrow to indicate the wind direction. https://en.wikipedia.org/wiki/Weather_vane

The one to the left is an "anemometer", a device used for measuring wind speed and direction. https://en.wikipedia.org/wiki/Anemometer

  • $\begingroup$ Balls are solid so anemometer is out. $\endgroup$ Commented Nov 21, 2021 at 3:19
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    $\begingroup$ Well, given the comments, we could edit to say " ... is supposed to be an anemometer but the props crew screwed up" $\endgroup$ Commented Nov 22, 2021 at 18:14
  • $\begingroup$ @CarlWitthoft Movie magic. $\endgroup$ Commented Nov 22, 2021 at 21:48
  • $\begingroup$ It is disgusting, someone is messing/deleting comments without proper notification. $\endgroup$
    – r13
    Commented Nov 22, 2021 at 21:56
  • $\begingroup$ @r13 I believe Carl is referring to comments on OP question! $\endgroup$ Commented Nov 22, 2021 at 23:51

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