relation between the cross sectional area of the header and cross machine direction position as shown in the graph of fig2 the height at the recirculation end is typically calculated in relation to the height at the inlet end to give ten percent recirculation the straight line header 46 results in a change in cross sectional area from the inlet 47 to the recirculation outlet 48 that is constant as the area decreases the header 14 of this invention on the other hand has a change in cross sectional area per unit width of the headbox which is not constant but which increases as the header approaches the recirculation side this type of header is known as a parabolic header yet the parabolic distribution is achieved without any curved plates in the header construction the parabolic distribution is a consequence of the fact that the cross sectional area of the header is the product of the height h and width w of the headbox at any given point moving in the machine direction from one end to the other of the header both the width and the height of the header with respect to position in the cross machine direction x cd at any point along the header are described by linear equations because the height of the header has a negative taper the linear equation describing the vertical dimension of the header will have negative slope m 1 such that the height of the header will change from an initial height h inlet in a decreasing linear fashion with distance in the cross machine direction the width of the headbox has a positive taper or a positive slope m 2 and therefore the width increases from an initial width w initial with increasing position along.