1. An apparatus that uses the sun's rays reflected by a mirror to send messages in Morse code over long distances.
Usage: historical; military
2. A photograph made by the action of sunlight on a chemically treated surface.
Usage: archaic; photography

1. To send a message using a heliograph.
Usage: historical; military
2. To photograph using sunlight on a chemically treated surface.
Usage: archaic; photography

Examples

• The soldiers used heliographs to communicate across the desert during the military campaign.
• Before radio technology, heliographs were essential for long-distance communication in remote areas.
• The officer heliographed the message to the distant outpost in less than an hour.
• Early photographers experimented with heliographs to capture images using only sunlight.
• The heliograph reflected sunlight to transmit signals visible from miles away.