423 



THE STRENGTH 



the Edinburgh Journal of Science, will, if 

 needed, throw additional light on the matter. 



16. I took a board ABCD, 



3 feet 6 inches long, and 1 foot broad ; and 

 at about half the distance between its two 

 ends, and near to the side AB, there were 

 small moveable pullies affixed, as G, H, I, and 

 similar pullies near the corner C, as represented 

 on the figure; and in the intermediate space 

 between these, as at F, there was a rectangular 

 hole cut through the board, and where the 

 dotted line is seen, there projected the ends 

 of a number of equal equidistant straight 

 springs of iron or steel wire, which were 

 firmly inserted at their other ends into a wooden 



A_ _c frame abed, and this 



frame was then fast nailed 

 at its ends a and d to the 

 back of the board, so that 

 the springs between a and d might project about 

 an inch through the hole F, and be perpen* 

 dicular to the plain of the board. 



