Page:Pyrotechnics the history and art of firework making (1922).djvu/152

 greatest number fall in Class II, even though they may at first glance appear to belong to the first class.

Class I includes accidents caused by the accidental presence of fire and accidents caused by necessarily more or less violent action in manufacture, that is to say, in charging.

Ignition during charging may be caused in two ways, either by a blow on composition between the charging tool or drift and the spindle or other hard surface, or by heat generated by repeated blows on the consolidated composition.

In this class also should be put accidents, of which there are many, caused by playing or scuffing by the workpeople, the absence of safety overshoes, the presence of grit or iron or steel implements, in fact those caused by misconduct or negligence on the part of the workers, also the rare occasions where lightning has been the cause.

Accidents caused by slight friction have to a great extent ceased to exist owing to the elimination of chlorate and sulphur compositions. Where accidents arise owing to instability of the composition, they most frequently at the present time fall within Class II, as the instability of the composition is generally due to the presence of some impurity in one or more of the ingredients.

Another source of accident of this class is the use of violence in emergency with a composition which, although not sufficiently stable for heavy charging, is quite safe for careful manipulation; as for instance, where force is exerted to clear a funnel which has become blocked with composition, or some similar action.

As regards the part played by heat in accidents of this class, a study of the records clearly indicates how great is the influence of weather. By far the greatest number of accidents take place in the summer months; hot weather and a heavy