<prompt> The Heidbrink meter in Boyle;s machineReduces pressure of gasesIndicates flow of gasesIndicates humidity of gasesIt a fixed orifice meter  <response>: Heidbrink is a flowmeter used in past. It consists of a metal tapered tube with inveed black float. The upper-end projects in the glass tube. Other type of flowmeter used in past was Connell which has round bobin. 