6 Wilson and Weston, Torpedo- Boat Destroyers. 



((5) By reason of the term under the bracket becoming 

 great. On reference to Diagram i it will be seen that 



this term becomes infinite in magnitude when — = 2"36. 



Hence a second critical velocity 



which is a considerably lower velocity than the one above. 

 In actual practice it appears that the term is small 



compared with ^y^EI for all ordinary velocities, and may 



be neglected, in which case the coefficient outside the 

 bracket in equation (i) becomes equal to half the statical 

 stress, calculated on the assumption that the vessel is 

 supported on a wave of length equal to its own length, 

 with the crest in the centre (see Diagram 2). 



— &Ti^E.a&Efe '■>' HiGM Speed Ve.tvSEi-t 



'The lime of free vibration of a liar ends free-free is 



and in its gravest mode this becomes 



3'55 V gEi 



The second value of v gives for the period of the waves 

 L L'' 



,omes 



r55 V g^ 



'^-v-ysA 





i.e., the first critical perifxl is when the period of the forced vibration = 

 period of free vibration of the bar as a whole. See Kaylcigh's Sound, 

 Vol. I., p. 273. 



