Fernando Cabral wrote:
>As far as I know, what you call "heliograph" we just call
>"mirror". Nevertheless, there can be other names and usages
>if you check with the different armed forces and other people
>with survival training.
>
>As to me, the only name I know is really "mirror", even for
>those especially-made mirrors with a small hole in the centre
>(to be used to collimate the light ray).
>
>Again, since you can clearly use such a device to send
>Morse code you can say you "write" with the sunlight,
>than calling it "heliograph" should not be unacceptable.
I'm attaching a tiny JPEG illustration, taken from an ancient
dictionary, which accompanies the definition of 'heliograph'. The
instrument definitely has a mirror! But as you'll see, it also incorporates
a telegraph key and a sighting vane. My recollection is that they were
used by military forces in the 19th century in places like India. (I have
a half-baked recollection that Kipling refers to one in a poem...¿Is that a
source?!)
cheers,
Peter
Attachment converted: MAC Hard Disk:heliograph.JPEG.jpg (JPEG/GCon) (000176FF)
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Peter Mayer | [EMAIL PROTECTED]
Politics Department |
University of Adelaide | 'phone:+61.8 8303 5606/5610
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