Although the described device became commonly known as the Campbell-Stokes Sunshine Recorder, that term is best applied to recorders that use a curved and grooved support for the paper strip, as this was the variation described in 1880 by Sir George Stokes.
J. F. Campbell in 1853 developed a "self-registering sundial" that used a water-filled glass globe mounted in a mahogany bowl; the sun path charred a path in the bowls, which were replaced only twice a year, at midsummer and midwinter. Campbell obtained a solid glass sphere only in 1857 to prevent damage by freezing. True glass spheres became available to Campbell in about 1875. Campbell had originally proposed using a paper ribbon fastened to the inside of the bowl with rubber cement; for some reason he abandoned this strip and used just the bowl surface, replacing the entire bowls twice a year. By 1875 forty-eight charred bowls were available for analysis. In 1877 one R. H. Scott revived the original Campbell paper ribbon idea after realizing that a hemispheric bowl was not needed and described holding the paper with clips to the inner surface of a ring concentric with the spherical lens. Enter George Stokes whose sole contribution appears to be the description in the 1880 Quarterly Journal of the Meteorological Society of a double-grooved or slotted holder into which could be inserted the cardboard strips. Nevertheless, the device became widely known as the Campbell-Stokes Sunshine Recorder, completely overlooking the significant contributions of Scott. I am the proud owner of a Campbell-Stokes Sunshine Recorder and admire both its elegance and history. Now, one might wonder why the British were so interested in measuring the duration of daily sunlight! After all, by 1879 the Meteorological Council had at least twenty glass spheres burning paper strips. That's twenty data strips per day. Think of the data overload! Of course, the Campbell-Stokes Sunshine Recorder is only one of many kinds. Negretti and Zambra, for example, offered for sale in 1886 a Jordan's Improved Recorder using ferroprussiate (blueprint) paper inside a cylinder. This cylinder had two small holes, slits actually, that exposed the paper, one slit for morning and one for afternoon. Earlier versions of this recorder were described as early as 1839. I trust the group will forgive my ramblings about sunshine recorders. After all, they do indeed resemble sundials, which in fact, they are! > Does anybody know the name the device described below? > > It looks like a glass sphere held in the center of a small equatorial > sundial. The image of the sun focuses to a point at some short > distance away from the surface of the glass sphere. Held in place > at this distance away from the glass and following the curve of > the sphere is a piece of waxpaper against a dark background. > When the sun shines, the waxpaper is scorched. When the sun > is behind the clouds, it is not scorched. The result is a recording of the > amount of sunshine seen at that location on that day. -- Best wishes, Larry McDavid W6FUB Anaheim, CA (20 miles southeast of Los Angeles, near Disneyland)
