[FONT="]The insignia represents not a bomb, but an iron hand grenade with a powder charge and a fuse which had to be lit before throwing.
The Shell and Flame is considered the oldest branch insignia in the U.S. Army. The use of the Shell and Flame by the Ordnance Branch dates back to 1832. It was also used by the Artillery Branch until 1834 when the Artillery branch adopted the crossed-cannons as its branch insignia.
More info here: History of the Shell and Flame for the U.S. Army Ordnance Corps
Don.......... [/FONT]
Yep. Grenade (from the French for "pomegranate", or Latin "granatum" for the same fruit (with a lot of large seeds)) came to be the identifying emblem of the Grenadiers (who carried, lit and threw them). The British, French and German armies all chose the tall guys for these outfits - because they had to be strong enough and tall enough to light the fuse and throw the darned things far enough they wouldn't hurt their own troops! So Grenadiers came to be known as elite troops.