An Essay on the Signs of Ideas. 269 
There are some gestures, which seem to 
be mere arbitrary signs, and not, like those 
mentioned above, natural expressions of ideas, 
but which are of so long a standing, that it 
is almost impossible to trace their origin. 
Of this kind, is the uncovering of the head, 
which, although among Europeans, the most 
usual mark of respect, is probably the remains 
of some ancient custom. At present, the 
practice is without the shadow of a meaning, 
except asan arbitrary sign of respect. Of 
the same kind, is the custom of carrying: the 
hand to the mouth by way of salutation; 
the origin and meaning of which seem in- 
volved in obscurity. Mr. Gibbon* says, that 
it is the root of the latin word adoro, adorare, 
and that from the first books of Herodotus, 
it appears to be of Persian origin. But, 
upon looking into Herodotus, at that part 
where he describes the Persian modes of sa- 
lutation, 1 find he mentions nothing of the 
custom in question. 
T he various expressions of the countenance, 
arising from the action of the muscles of the 
face, may be considered as so many gestures, 
which are the signs of certain ideas, or trains 
* Decline and Fall of the Roman Empire, Vol. 10. Page 
124, Note. 
