An inexpensive positive temperature coefficient thermistor has metal terminals which have been miniaturized without deteriorating the characteristics or sacrificing the reliability of the device. A thin guard of a hard, flexible material passing around the rider’s ankle is retained at the outside of each sock, extending from the top of the sock to a line proximate the top of the shoe upper so as to protect the inside and outside of the ankle joint. The wagering increases the progressive jackpot award. A carbon dioxide separator is also included in the apparatus that receives combustion gases exiting the bottoming cycle unit and separates carbon dioxide from the other combustion gases. 40\xb0\u2266\u03b8ave\u226670\xb0 is satisfied where \u03b8ave is an average value of axial angles of the two layers.