with Reference to Sound. 361 
distance of seventy-five feet it will be as plainly heard at a dis- 
tance of ninety-two feet in front of him, declining in strength 
behind him so as not to be clearly heard at much more than thir- 
ty feet. The following diagram will aid us to understand this ; 
the position of the speaker is represented by the point of inter- 
section of the straight lines.* 
: 2, 
a 
% 
75 ft. 75ft. 
| 92 ft. - 
The figure that would conform to these measurements it will 
Seen is an imperfect ellipse whose major and minor axes are 
spectively 150 and 122 feet. This is the space allotted to the 
“ound in the ordinary exertions of speaking, and under the usual 
onditions of the atmosphere. We have seen, however, that, 
When the medium is in a state of absolute purity, vocal sounds 
ii teadily conveyed over an extent far greater than that just sta- 
led. We shall have occasion to allude to this point again when 
We come to the subject of ventilation and warming. 
The calculations of Mr. Wyatt, we repeat, refer only to the 
Power of the vocal tones in the ordinary efforts of articulate 
Speech ; but of the capacity of the human voice, when rightly 
: * Vide Gwilt’s Encyclopedia of Architecture. 
"conn Serres, Vol. XV, No, 45,—May, 1853. 47 
