British Army uniform and equipment in World War I It contained an inner can of explosive with an outer can of metal fragments or ball bearings. The fuses that were developed for the Jam Tin Grenade were activated by friction or a by lighted taper which was often replaced by a lighted cigarette. This was followed by the highly successful Mills bomb in 1915. It was oval in shape to fit into a clenched fist and time fused. The detonator was activated by a spring driven firing pin which was restrained by a lever that in turn was locked by a safety pin. The Mills bomb was a defensive
Safety in numbers Safety in numbers Safety in numbers is the hypothesis that, by being part of a large physical group or mass, an individual is less likely to be the victim of a mishap, accident, attack, or other bad event. Some related theories also argue (and can show statistically) that mass behaviour (by becoming more predictable and "known" to other people) can reduce accident risks, such as in traffic safety – in this case, the safety effect creates an actual reduction of danger, rather than just a redistribution over a larger group. The mathematical biologist W.D. Hamilton proposed his selfish herd theory