Any parish councils, or parish councils and county councils or district committees or town councils or burgh commissioners, may, from time to time, join in appointing, out of their respective bodies, a joint committee for any purpose of this Act in which they are jointly interested, and the provisions of section seventy-six of the principal Act, with regard to the appointment and powers of joint committees of county councils, or of county councils and town councils, shall, with the necessary variations, apply to joint committees appointed under this section.