Long Tom Canon

The 155 mm Creusot Long Tom was a French siege gun manufactured by Schneider et Cie in Le Creusot, France and used by the Boers in the Second Boer War as field guns.: p. 164 

Four guns, along with 4,000 common shells, 4,000 shrapnel shells and 800 case shot were purchased by the South African Republic in 1897. The guns were emplaced in four forts around the country's capital, Pretoria.

Source: Wikipedia