Now, if for the present we only take into account the energy 
supplied and neglect the necessary loss of energy in the organ pipe 
and in the air; if we further assume the validity of the theoretical 
law of distances (extension over a hemisphere), we obtain the following. 
results : 
1. that the sensitiveness of our ear has only one maximum, 
ving in the four times marked octave. 
2. that there is a zone of fair sensitiveness, extending from gq’ to g’. 
€ 
3. that outside this zone the sensitiveness diminishes very rapidly. 
4. that in the zone of fair sensitiveness the perceptible minima 
are of the same order. 
5. that, for the most sensitive part of the scale the perceptible 
minimum is 0,32 >< 13-8 ergs for Mr. Quix, 1,9 « 10-8 ergs for myself. 
The true perceptible minimum for the most sensitive point of the 
scale will of course lie lower. How much lower cannot be determined 
for the present, but at any rate the perceptible minimum found with 
organ pipes certainly remains a million times greater than that which 
was calculated by Max Wien from his telephone experiments. The 
minima, found on the heath and in the library, are in satisfactory 
agreement, however, with the minimum which we formerly caleu- 
lated for tuning-forks, using the data of TépLur and BOLTZMANN '). 
Taking into account the “efficiency” of an organ pipe, found by 
Weester (0,0013 and 0,0038), the perceptible minimum for the 
most sensitive point of the scale becomes lower, namely 0,45 to 
1,3. 10—-"" ergs, but it does not reach the amazingly small value of 
Max Wren’s telephone experiments by a long way. Even if we 
assume that one hears better at night in the profound silence of a 
laboratory, than on the heath, not to mention an afternoon hour in 
the library, yet this difference is by no means accounted for. But I 
see no reason why the results of experiments made on perfectly 
level ground, far from woods or buildings, which, according to 
Max Wien’s former valuable investigations, fall perfectly under the 
theoretical law of the distribution of sound, should deserve less 
confidence than experiments with a telephone, which require very 
complicated calculations. 
1) Töprer u. BoLTZMANN. Ann. d. Physik u. Chemie Bd. 141 p. 321. 
