Since the mysterious explosion which occurred in a candy manufactory in this city a few weeks ago, attention has been turned to various other singular explosions which have taken place in past years, and investigations seem to lead to the conclusion that the dust of any inflammable substance, when mixed with air in a certain proportion, is liable to explode Many instances are mentioned in proof of this theory. In 1872 a flour explosion was caused in a factory at Glasgow by sparks from the millstones. About four years ago an explosion of sawdust occurred in Friedelc, Germany; and it is on record that a cloud of flour dust was ignited by a candle in the Ofen Pesth steam mill, in Austria, causing a terrific explosion. A disastrous explosion followed the ignition of sawdust in the Pullman car works at Detroit about two years ago, and a similar casualty occurred in the works of the Millburn wagon company at Toledo. Finely pulverized cork is said to have caused an explosion in a factory on Staten Island. It appears that the fine dust of flour, bran, starch, wood, etc., may in certain conditions become explosive, and it is suggested as probable that the impalpable dust of starch doubtless present in several rooms of the candy manufactory may have been the cause of the mysterious explosion in Barclay street.