From Preface: "The present bulletin is printed as a supplement to Bulletin 17 and is intended primarily for coal miners, especially for those working in fields where inflammable gas or coal dust may cause disastrous mine explosions. The bulletin is issued by the Bureau of Mines in the hope that it may prove helpful in lessening accidents due to the use of explosives, and in particular may aid in preventing mine explosions, many of which have been caused by the use of improper explosives."