C. M. CHILD. 



that the piece rolls up spirally on its longitudinal axis. Such a 

 case is shown in Fig. 17 ; here the inner and outer coils of the 

 spiral are on the same level at the outer end of the piece. Fig. 

 19 shows a spirally coiled piece in which the inner coils are 

 higher than the outer. Figs. 18 and 20 represent longitudinal 

 sections of one end of these pieces and Fig. 2 i a transverse sec- 

 tion. 



The Figs. 1 121 represent only the chief types resulting from 

 pieces like Fig. 10. All possible intermediate forms and modifi- 



FIG. 13. 



FIG. 15. 



FIG. j i . 



FIG. 



14- 



FIG. 16. 



FIG. 10. 



cations of these different types occur, the differences depending 

 on various conditions, but chiefly on the relative rapidity of the 

 inrolling in the different directions. 



Semi-cylindrical pieces or longitudinal strips may roll either 

 longitudinally or transversely. The greater the length and the 

 less the breadth of the strip the more likely it is to roll trans- 

 versely. Figs. 2224 show a strip and two forms of trans- 

 verse rolling which it may undergo. The longitudinal strips 



