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 atmosphere are the most likely conditions to produce trouble for the pyrotechnist, although whether the primary cause is heat or owing to an electrical condition of the atmosphere it is difficult to say, probably it is the two conditions in conjunction. Sulphur and shellac, two very important ingredients in the art, are both capable of holding an electric charge, and it seems not unlikely that they may be so charged in an electric atmosphere during the process of mixing. Accidents in Class II are generally less easily explained than those in the former class and have occurred in many forms. As has been said, during the period (about sixty-five years) from the introduction of chlorate of potash to the Order in Council forbidding its use with sulphur, numerous accidents occurred; spontaneous ignition, both whilst drying during manufacture and even during mixing, ignition from very slight friction, and for a time a frequent occurrence the detonation of the contents of shell by the lifting charge. During the period of seventeen years between the date of the Explosives Act and the prohibition of chlorate sulphur mixture, twenty-eight accidents are recorded, resulting in eleven deaths attributable to the use of such mixtures. The instability of chlorate sulphur compositions, however, does not appear to be so much due to the presence of these two chemicals themselves, but rather to the presence of impurity in conjunction with them. Commercial sulphur often contains free sulphurous acid, which acting upon the chlorate produces chlorine tetroxide, which rapidly decomposes and ignites the mass of the composition. Other acids which produce decomposition of the chlorate are equally likely to produce ignition. Of such cases, examples may be mentioned of acid being present in the paste used for case and box-making, also in gumwater which has been kept some time before using, and in starch paste similarly treated. Spontaneous ignition has also been caused by the contact of oil with finely divided carbon such as lampblack or finely divided metals, such as magnesium and aluminium, which are so largely used at the present time.