Thallium

Thallium, a rare metallic element similar to lead, but heavier, discovered in 1861 by the green in the spectrum in the flame as it was being volatilised.

Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)

Thalia * Thames
Tewfik Pasha, Mohammed
Tewkesbury
Texas
Texel
Tezcuco
Thackeray, William Makepeace
Thaïs
Thalberg, Sigismund
Thales
Thalia
Thallium
Thames
Thane
Thanet, Isle Of
Thasos
Thaumuz
Théâtre Français
Thebaïde
Thebans
Thebes
Thebes