Abstract: To measure the opacity of sheet material, such as paper, a beam of light is directed against the material and the intensity of any light passing through the material is sensed and converted to a visual readout. A plurality of opacity measurements are made at different areas on the sheet material and, when a selected number of measurements have been made, a readout of the average value of the measurements is generated. The particular technique enables a large number of opacity measurements to be quickly and conveniently made and averaged, and is considerably less complicated and time consuming than opacity measurements which are conventionally made as a function of contrast ratios.

Abstract: A liquid cooling tower has liquid distribution nozzles that spray liquid to be cooled away from the sides of the fill chamber. The spray pattern is restricted to less than about 180.degree.. This prevents liquid from being sprayed out of or on to the tower or from being carried out of or on to the tower by the air flow. The nozzles have a single large liquid discharge opening so that solid objects that flow in with the liquid will not clog them.