Category:Helmholtz double siren

Media in category "Helmholtz double siren"

The following 2 files are in this category, out of 2 total.

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  Helmholtz double siren, F. Sauerwald, Berlin, c. 1870 - Putnam Gallery - Harvard University - DSC08074.jpg 3,631 × 5,138; 7.69 MB
  
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  Helmholtz's double siren.jpg 333 × 500; 111 KB