438 APPENDIX. 



If, for instance, the temperature read off is 74.75, and the appa- 

 rent strength 81 f per cent., the true strength belonging to 81 per 

 cent, and 74.75, which is = 78.4, is first found in the table and to 

 this is added the fraction f = 0.75 or sufficiently accurate = 0.7. 

 This gives 78.4 + 0.7 = 79.1 per cent, as the nearest accurate true 

 strength. 



