 To guard against the possibility of a flame travelling back through the incoming gases (an explosive backblast), air ingress was by a number of small-bore orifices through which the air flowed at a velocity higher than the velocity of the flame in a mixture of firedamp (mostly methane) and air.The body of the lamp was lengthened to give the flame a greater convective draw, and thus allow a greater inlet flow restriction and make the lamp less sensitive to air currents.Davy had originally attempted a safety lamp on similar principles, before preferring to enclose the flame inside a brass gauze cylinder; he had publicly identified the importance of allowing the restricted airflow in through "small" orifices (in which the flame velocity is lower) before Stephenson had, and he and his adherents remained convinced that Stephenson had not made this discovery independently.