AMERICAN ORIGINS 1920, Visible pumps - Eventually, the pump was assigned the single task of drawing the liquid, while the job of measurement passed to the vessel, and thus began the era of "visible pumps." The apparatus was most impressive to behold: a sturdy housing concealed the pumping unit which, no longer linked to measurement, could be driven by an electric motor; above stood the measuring vessel, and on top of it all towered the globe. These vessels were enormous at first: the earliest ones carried five American gallons, by the Twenties they grew to ten, and in some cases held as many as fifteen. In Canada, one could find pumps with two vessels of ten imperial gallons each, for the dispensing of two different types of fuel (American gallon = 3.7853 liters; imperial gallon = 4.5460 liters). The classic vessel for what came to be called the visible pump was numerically graduated in increasing order toward the bottom. It functioned by filling itself completely, after which a valve was opened and the fuel began to flow; when the liquid level reached the number corresponding to the amount requested, the shutoff valve -at first positioned above the hose and later (circa 1924) incorporated directly into the nozzle- would close. 6/20