[wert] . VISCOSITY IN LIQUIDS 103 
7. The advantage, if any, of working with a standard head of pres- 
sure. The effective head is 3 inches. Is it desirable to take a 3-inch head 
of water as a standard, and to take the level for other liquids inversely 
as their density, so that 
1,000 
head in inches= ART 3 
C[ 
si ; : SAUER Be 
when d is the density of the liquid ? 
I have arranged the index which marks the level of the liquid in such 
a way that this change of level can easily be made if found decirable. 
