     /*
      Base unit - watts
      */
-
-    public required init(symbol: String) {
-        fatalError("init(symbol:) has not been implemented")
-    }
-
-    public required init(symbol: String, converter: UnitConverter) {
-        super.init(symbol: symbol, converter: converter)
-    }
     
     private struct Symbol {
         static let terawatts  = "TW"

        self.init(symbol: symbol, converter: UnitConverterLinear(coefficient: coefficient))
    }
    
    
    open class var partsPerMillion: UnitDispersion {
        get {
            return UnitDispersion(symbol: Symbol.partsPerMillion, coefficient: Coefficient.partsPerMillion)

    /*
     Base unit - ohms
     */
    
    private struct Symbol {
        static let megaohms  = "MΩ"
