The winding treads must be made of uniform width around the cylinder, so as to obtain a uniform curve in the rail. It will be observed that there is a 5-inch width introduced between the straight flight and the cylinder, which provides for a better easement, or ramp, from the pitch of the straight rail into the steeper pitch of the wreath rail; besides, if the winders were all contained in the cylinder, it would make a sudden and abrupt change of inclination in the stairway, causing travelers to stumble and fall.