When the signal stations were established in 1818–1819, it became the key link in the chain, passing signals from Highgate east to Moncrieffe on the cliffs of the St. John/St. Philip border, and north to the Cotton Tower, Grenade Hall and Dover Fort (and vice versa). But Gun Hill was also the typical 'Hill Station' of the tropics, used as a convalescent station for the troops, and for evacuation of the Garrison in times of epidemics of yellow fever and once (in 1854) of cholera. There was only a small barrack, and a mass evacuations went under canvas.