The purpose of this letter is to present an improved version of one of the enclosure demonstrations previously reported as a part of a paper in this journal.1 Specifically, I am referring to the double-layered enclosure containing air and two different colors of glycerin, blue in the front and yellow in the back. The new version has two modifications. First, a horizontal partition with two gaps (1/4-in. wide, each) is added in each layer. The role of the partition is to slow down the exchange between the glycerin and air, and therefore provide for a longer time to observe the demonstration. Second, the blue-colored glycerin is diluted by adding (on volume basis) 10% water, whereas the yellow-colored glycerin is not diluted. The dilution significantly (and nonlinearly) reduces the viscosity. As a result, the blue glycerin flows through the gaps faster than the yellow glycerin. For comparison at 20 °C,...

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