23 



which a snake produces in its body during loco- 

 motion. 



For future nomenclature, we may liken each 

 division of the flexures, although the curvature be 

 not in a single plane, to the letter S, and we shall 

 then have an ess proper and an ess reversed al- 

 ternately throughout the series. 



If we next completely untwist the piece of whip- 

 lash, and then, with the dii'ections of the counter- 

 turns exchanged, twist it again, we shall have 

 similar results, with the only exception that where 

 the curvature was a proper S, it will now be a 

 reversed S, and vice versa. In other words, re- 

 garding only the lateral aspects, where there vras a 

 concavity to the right we shall have a concavity to 

 the left, and where there was a convexity to the 

 right we shall have a convexity to the left. 



We shall call each separate section of torsion an S, 

 half a section a C. 



§ 15. Were the piece of whip-lash of perfectly 

 uniform consistence, and were all the rectilineal 

 elements of its cylinder drawn mth exact equahty 

 of force, it may be shown, we think, that a series 

 of somewhat one-sided cones, alternately point to 

 point and base to base, would be the result. But 

 by twisting it in the manner described, one set of 



