212 DR. LOUIS YESSOT KINO ON THE PROPAGATION OF SOUND IN THE FREE 
Section. Page 
13. On the thermodynamical measurement of acoustic output— 
(i.) Experimental arrangements.239 
(ii.) Sources of error in the measurement of temperature.241 
(iii.) Discussion of the Father Point tests.244 
14. Summary and conclusions.245 
Appendix I.— On the Acoustic Characteristics of the Webster Phonometer 
as Employed in the Measurement of Sound from the Diaphone. 
(i.) Determination of phonometer constants.248 
(ii.) Calibration of phonometer resonator for pitch.249 
(iii.) Determination of phonometer resonance curve with respect to the sound waves generated 
by the diaphone.251 
(iv.) Determination of the pitch regulation of the diaphone. 253 
(v.) Note on the quality of the sound emitted by the diaphone.254 
Appendix II.— Acoustic Surveys in the Neighbourhood of the Father Point 
Fog-Signal Station. 
(i.) General procedure in taking observations.255 
(ii.) Description of tables and charts.256 
(iii.) Discussion of results of acoustic surveys— 
(1) Acoustic gradients. .... 265 
(2) Distribution of sound over circular courses.267 
(iv.) Note on acoustic shadows.268 
Acoustic surveys August 26 to September 20, 1913—- 
Tables of observations 1 to 14...269 
Appendix III.— On the Thermodynamic Measurement of Acoustic Efficiency. 
(i.) General procedure in taking observations..286 
(ii.) Measurement of pressure and air consumption.287 
(iii.) On the measurement of temperatures..288 
Tests Nos. 1 to 5, September 13 to 16, 1913— 
Tables of observations ..289 
Part I.—ON THE MATHEMATICAL THEORY OF THE PROPAGATION 
OF SOUND IN A HOMOGENEOUS ATMOSPHERE WITH SPECIAL 
REFERENCE TO WAVES OF LARGE AMPLITUDE. 
§ 1. Introduction. 
The theory of the propagation of sound-waves of small amplitude such as are 
produced by ordinary acoustic instruments has received repeated experimental 
verification on almost every point. Over such distances as are available for indoor 
experiments, the atmosphere may be regarded as a homogeneous medium of constant 
temperature. The variations of pressure in such sound-waves are so small that the 
