The effect of personal equation on measurements of the solar semi-diameter by transit circle observers

Cape Observatory transit circle measurements of systematic trends in the semi-diameter of the sun (1834, 1861-1871, 1884-1892) are considered, and an analysis of Washington six inch observations (1899-1903, 1911-1918, 1956-1971, 1975-1981) is given. A discordance between horizontal and vertical results in Cape measurements implies that these measurements are inaccurate due to the use of personal equations. The Washington measurements consider observational corrections and instrumental techniques, and it is thus concluded that no secular change in solar diameter has occurred.