A SUMMARY OF PROCEDURE 31 
The arrangement of apparatus for the use of the 
quantitative method is indicated diagrammatically in 
Fig. 8. The diagram is self-explanatory. As an addi- 
tional guide, a photograph of a set of apparatus in actual 
use is reproduced in Fig. 9. In the final chapter of the 
book various precautions are described which much ex- 
perience with the method has suggested. 
