THE EIFFEL TOWER, 



149 



Expermiental verification. — [This model, and one like it, 

 shown during the reading of the paper, were executed for 

 me by the kindness of Mr. (now Professor) Selman.] Let AB, 

 BC, CD {Fig. 5) be three freely hinged rods, which stand 



Fig. 5. 



for any section of the tower, and let E, a perpendicular to 

 BC, rigidly fixed to it, stand for the rest of the tower. Let 

 P, Q, E,, be strings fastened at various points, which can bs 

 pulled so as to represent the action of the wind on the part 



we obtain- 



dv J 

 x—ax 



=a:- -^, or integrating the left hand by parts- 



V ay 



dx 



I 



XV —Jvdx y 



V dy 



dx 



vdx^y^ or ^ = -^ 

 V dy dz dy or 

 dx dx dx 



