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engaged on those labours at the Washington Observatory which will immortalize his name, Maury frequently ventilated his ideas and the results of his ripe experience in periodical literature.

In 1843 he wrote on the subject of "Lighthouses on the Florida and Gulf Coasts, and showed just where they ought to be placed. In another paper, in the same year, he begged that a competent officer of the navy might be sent to Memphis, or elsewhere on the Mississippi River, to make systematic observations on the rise and fall of the water in that river and its tributaries. For this purpose Lieutenant Marr was selected, and directed by Maury to make an accurate cross section of the river opposite to the navy yard, and to observe for 365 consecutive days the velocity of the current near the surface and bottom, for the purpose of ascertaining the volume of water passing that point daily; also to take daily a measured quantity of water, evaporate it, and note the amount of silt or solid matter it contained.

He was to observe daily the temperature of the air and water, the amount of evaporation and precipitation. The first year the continuity of the series was broken, and he had to begin again and go over the work, so as to have a complete series of observations for one year. "These observations, patiently and carefully made and afterwards digested by