A considerable revenue has thus annually been derived. Other electrical apparatus of the observatory was modified and improved. A “switch-board,” the device of his predecessor was much elaborated in its mechanism, whereby the electrical current was made more available and all the principal instruments were connected at will with the chronographs. In 1868 when he visited Europe he procured the apparatus of a meridian circle of the latest device, the lenses being made in Cambridge. In setting up the instrument he saw opportunity to introduce various improvements in mechanism. These were approved by experience and went into general use elsewhere. Another of his devices was “for the determination of absolute personal equation by mechanical means.” Other contrivances, either wholly original or ingenious modifications of known apparatus, were an attachment to the spectroscope for automatic recording, being a modification of the chronograph: a combination of a stationary plane mirror with a fixed lens of great focal length—from 30 to 40 feet—for photographing the sun; a later improvement of this, by which the telescope was reduced to a single fixed lens of long focus and small aperture, chromatic aberration was avoided and the image on the plate could be made as large as was convenient for measuring; and a change of method by which the sun’s image could be taken at the principal focus of the object glass and not beyond an eye-piece used to enlarge the image. In February, 1866, when he took charge of the observatory, the great equatorial was applied to a series of observations of double, and especially binary stars. This investigation was continued as steadily as circumstances would permit till 1872, and the results appear in the annals. In 1867 the first spectroscope owned by the observatory was imported, and in 1869 another. Two small direct vision spectroscopes were also procured during Prof. Winlock’s term. In 1870 the new meridian circle, a superior instrument, was set up, and on Nov. 10 of that year was begun the series of observations for position of stars in the “Cambridge zone,” so called, or that between 50° north and 55° north and overlapping 10′ upon each contiguous zone. This survey was a joint enterprise conducted by certain of the great observatories of the world, that of Harvard being one of the two in this country having a share in the work. On July 4, 1870, was begun a series of photographs of the sun, and the work was continued nearly or quite to the end of Prof. Winlock’s term, many hundred photographs being comprised in the list. [Illustration: HARVARD OBSERVATORY STATION IN SPAIN.]