DIY History | Transcribe | Scholarship at Iowa | Theory of the astronomical transit instrument applied to the portable transit instrument Wuerdemann no.26: a compilation from various authorities, with original observations by Harry Edward Burton, 1903 | Theory of the astronomical transit instrument applied to the portable transit instrument Wuerdemann no. 26: a compilation from various authorities, with original observations by Harry Edward Burton, 1903, Page 21

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Theory of the astronomical transit instrument applied to the portable transit instrument Wuerdemann no.26: a compilation from various authorities, with original observations by Harry Edward Burton, 1903

Theory of the astronomical transit instrument applied to the portable transit instrument Wuerdemann no. 26: a compilation from various authorities, with original observations by Harry Edward Burton, 1903, Page 21

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the reading of the north end and S that of the south end. Then the position of the middle of the bubble is S-N/2 south . S-N/2 is called the mean of the north and south readings and is just in a column headed "Means" Likewise N-S/2 is the mean when the bubble is in the north end of the tube. Before computing the position of the middle od the bubble turn the alidade tangent screw forward thus sending the bubble toward the north end of the scale. While the bubble is coming to rest, compute S-N/2. Read the level again. Let N' be the north reading and S' the south. The position of the middle of the bubble is then N'-S'/2 north. As a check, N+S should in general equal N'+S' since the bubble remains almost constant in length. It may gradually lengthen or shorten a little on account of change in temperature. Now the middle of the bubble has moved over the number of divisions of the scale given by S-N/2 + N'-S'/2, and in

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135122 the reading of the north end and S that of the south end. Then the position of the middle of the bubble is S-N/2 south . S-N/2 is called the mean of the north and south readings and is just in a column headed "Means" Likewise N-S/2 is the mean when the bubble is in the north end of the tube. Before computing the position of the middle od the bubble turn the alidade tangent screw forward thus sending the bubble toward the north end of the scale. While the bubble is coming to rest, compute S-N/2. Read the level again. Let N' be the north reading and S' the south. The position of the middle of the bubble is then N'-S'/2 north. As a check, N+S should in general equal N'+S' since the bubble remains almost constant in length. It may gradually lengthen or shorten a little on account of change in temperature. Now the middle of the bubble has moved over the number of divisions of the scale given by S-N/2 + N'-S'/2, and in