IOWA ACADEMY OP SCIENCE 
197 
As to tlie real value of the variator, it can be relied upon only as an 
instrument of approximate pitch and relative intervals. The fact that 
its pitch varies with pressure and mouth-piece position, and probably 
with temperature, humidity, and other conditions makes an absolute 
reading scale impossible. A variation in one of these conditions would 
throw any scale out of proportion. But even if it cannot be relied 
upon for careful quantitative work, it is a desirable piece of apparatus 
for the psychology laboratory. Its loud clear tone and ready manner 
of changing pitch make it especially valuable for general class experi- 
ments and tests. 
