Erratum in February Number, p. 160. 



For paragraph 3 of Mr. Hudson's paper (commencing " This point " &c.) sub- 

 stitute : — 



This point can be easily tested experimentally as regards sound. Thus a tense 

 string with amplitude of vibration = 2 ought to become inaudible at twice the dis- 

 tance at which it ceases to be heard with amplitude = 1, if the square of the am- 

 plitude be the correct assumption. The relative distances at which the sounds 

 should be inaudible ought to be as 1 to 0*70715, if the simple amplitude (not its 

 square) be correct. 



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