320 
IOWA ACADEMY OF SCIENCE 
be able to make certain discernments based on the intensity and 
duration of each pitch. 
Construction . — The standardization of the details of construc- 
tion is a matter that will have to be determined after much 
study. The smaller the number of crystals and corresponding 
pitched notes the easier it will be for the student to detect some 
of .the most characteristic letters, also the simpler and less ex- 
pensive will be the apparatus. On the other hand there must be 
enough variation in sound combinations to enable the reader to 
distinguish every character. Two crystals and two receivers 
may be sufficient. On the other hand as many as five or six 
may be advisable. Only experience can tell. 
If more than two notes are necessary these may all be heard 
in one receiver, which would be the usual practice. However, it 
may be that a greater distinctness and clearness may be obtained 
using two or. more resonating plates in one receiver as shown in 
figure 21 (Fig. 2). One or both ears may be used as experience 
will dictate. 
The Physical Laboratory, 
State University op Iowa. 
