An Enquiry for Hydraulic Engineers. To the Editor of FIRE AND WATER: I find quite a difference among engineers and waterworks officials in their rules for calculating the pressure per square inch of a column of water. The basis that every twenty-seven inches in the height of a column gives one pound pressure per square inch is one mode of calculation. Others multiply the height of the column in feet by 434 as a common factor; others use in the same way 231, etc. Now these rules of course give different results, and cannot all be correct. Will some competent hydraulic engineer give, through the columns of your valuable journal, a correct rule for obtaining the static pressure per square inch of a column of water at any given height ? ENQUIRER. NEW YORK, September 5.