I WAS interested to read the Looking Back feature 'Oh what a lovely war' (LET, January 28) with an illustration of a World War Two smoke generator.

It must have made breathing difficult and smelled nauseating when it was working.

During war, we had smoke generators, but they worked in a different way, giving smoke without fire. They were known as Smoke Cloud Installations -- cylindrical tanks about eight feet long and three feet in diameter.

They could be slung underneath aircraft and used for laying down a smoke screen, enabling troops and weapons to be moved about undetected.

These canisters had a hole in the front and back which were sealed by bakelite discs which, when smoke was needed, could be broken by an explosive detonator at the push of a button.

This allowed air to rush in at the front and the liquid to gush out at the back. The liquid used was stannous chloride which, on contact with moisture in the air, produced a huge amount of dense, white, relatively-harmless smoke which, when the air was calm, could hang around for several hours.

ALBERT MORRIS, Clement View, Nelson.