Hemisferium 30 minute hourglass
Hemisferium reproduction hourglass. Obtained from Spain.
This is a reproduction of a 16th century hourglass. These hourglasses were not used specifically in navigation but rather to keep overall time. 8 or these glasses would constitute a standard watch of 4 hours. This replica behaves much like the real thing in that it is around 30 seconds of from a true 30 minutes. This is due to manufacturing inconsistencies and cannot be remedied.
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Hemisferium reproduction hourglass. Obtained from Spain.