1890.] On Wind Pressure upon an Inclined Surface. 255 



frame, and accordingly the values for position It only were used for 

 drawing the curve. 



Rectangle 4 feet by 3 inches. 



The curve G, fig. 12, therefore shows the moment about 0, rather 

 than the normal component of the pressure, but, the strip being only 

 3 inches broad, the departure of the central line of pressure from the 

 centre of the strip cannot cause any very serious difference. The actual 

 pressure upon a surface of this kind is much greater than upon an 

 equal surface when collected in a compact form, such as a square or 

 circle, the difference in this case being more than 20 per cent. This 

 is quite in accordance with previous experiments that have been made 

 on the subject. 



The dotted line shows the value of the normal component given by 

 Lord Rayleigh, the curves being made to agree at the beginning and 

 end. The agreement between the theoretical and experimental curves 

 would be more marked if both gave the same quantity, for the moment 



