GENERAL MEETING. 13 
Mr. Jounson then read from Judge Brown’s opinion, extracts 
from papers read before the Washington Philosophical Society by 
three of its former Presidents, Henry, Taylor, and Welling, and by 
himself, all as to the difficulty of determining the direction of sound, 
and he congratulated the Society that its conclusions had been 
adopted by the courts. 
As it was evident that the unaided ear could not be relied upon 
to fix the direction from which sound came, Mr. JOHNSON said atten- 
tion should be directed to giving the ear all possible assistance. 
That something of this kind could be done was proved, he thought, 
by Professor Morton’s experimentation with the topophone. This 
instrument had been devised by Professor Mayer of the Stevens 
Institute of Technology. It consisted of an arrangement by which 
two Helmholtz resonators were connected on the deck of a steamer 
with rubber tubes running into the cabin and with bars and rods 
which could be moved from the cabin. The actuating principle of 
the device was the neutralization of the dynamic force of the full 
sound wave by the half sound wave, thus approximating silence, 
and thus indicating automatically, within ten degrees, or less than 
one point of the compass, the direction of the sound. 
Mr. Pau. remarked that the bar connecting the resonators should 
be shorter than the wave length of the sound under observation, 
since otherwise deceptive results would be obtained with the two 
resonators in similar phases of different waves. Mr. TayLor ques- 
tioned the utility of the instrument, though heartily applauding its 
ingenuity. The real difficulty in determining sound direction arises 
from the heterogeneity of the air in point of density and moisture, 
and especially from its indeterminate differences of movement, 
whereby diffractions and refractions are occasioned many times 
greater than those affecting light. The topophone, like the ear, is 
cognizant only of the final direction of the incident beam of sound, 
so to speak, and can tell us nothing of the direction of the source of 
sound. Mr. E. FarquHar remarked that the verdict of the ear in 
regard to direction is usually just; the conditions under which it 
errs are exceptional. He thought there was a rapid adjustment by 
motion of the head, from which the general direction is almost in- 
voluntarily ascertained. Mr. F. Baker said that animals, such as, 
for example, the carnivora, make fewer mistakes than man, and this 
is probably due to their muscular control of the external ear. When 
the ears are Becee up in listening, special tensions may be given 
