On Signals made by Fire . SOP 
and very justly ; for the experiment might have been 
made with little trouble to himself. 
* Pliny relates another method, which is not altoge- 
ther improbable. Deeimus Brutus defended the city of 
Modena besieged by Antony, who prevented his sending 
the least advice to the consuls, by drawing lines round 
the city, and laying nets in the river. However, Brutus 
employed pigeons, to whose feet he fastened letters, 
which arrived in safety wherever he thought proper to 
send them. Of what use, says f Pliny, were Antony’s 
intrenehments and sentinels to him ? Of what service 
were all the nets he spread, when the new courier took 
his rout through the air? 
Travellers relate, that to carry advices from Alexan- 
dria to Aleppo, when ships arrive in that harbour, they 
make use of pigeons who have young ones at Aleppo. 
Letters, containing the advices to be communicated, are 
fastened about the pigeons’ necks, or feet ; this being 
done, the pigeons take wing, soar to a great height, and 
fly to Aleppo, where the letters are taken from them. The 
same method is used in many other places. 
Description of the Instruments employed in Signals made 
by Fire , 
Mr. Chevalier, mathematical professor in the royal 
college, a fellow-member with me, and my particular 
friend, has been so good as to delineate, at my request, 
the figure of the instrument mentioned by Polybius, and 
to add the following explication of it. — Plate 8. 
In this manner I conceive the idea I have of the in- 
strument described by Polybius, for communicating ad~ 
vices at a great distance, by signals made by fire. 
* Plin, 1. vii. c. 37. 
f Quid vallum, et vigil obsidio, atque etiam retia amne pretext a profiler© Air 
tpnio, per coelum eunte nuntio ? 
