Botany and Zoology. 325 



lit :in<rl("^ to a wave-front it cannot vibrate, for both of its sides 

 >;iiiuiU:uuously acted on by impulses of the same phase and 

 (MHi:iI incioy ' Thus, by bringing the plane of a membrane 

 ) ili.u a/.iniiitb where it remains" at rest we shall have found 

 l>l,iiK' |ia^>ini>;- through the center of origin of the sound. I 

 I propose tlie use of two resonators, or of two ear trumpets, 

 '•<(1 at tlie ends of a long horizontal rod which rotates around 

 ( rticiil avis. I may thus obtain an increase in the aural paral- 

 I5y rotating the horizontal rod around its center I may be 

 ' to bring the two sonorous sensations either to disappear, or to 

 ome of equal intensity, and by these indications to arrive at 

 "lirei'tion of a sound. Tlie last mentioned idea may develop 

 ) something useful to the mariner who has to ascertain the 



II. BOTAJS'Y AND ZOOLOGY. 

 1. Botanu-'d CotitrifmtioHS, separatelv i-sued from the 

 (ele\enth) volume of the Frocfedhnjs of tho A>uerh'rm A 



:r;:' 



liome but not f ,i 



