GRAND VAN HEURCK MICROSCOPE (modified Rousselet Compressorium):

c. 1910

Maker: W. WATSON & SONS LTD.

A similar compressor was invented by Charles Rousselet, FRMS 'about 1890'. It was first noted and reported in the JRMS in 1893, but subsequently modified by Watson and others. These modifications gave slight increases in convenience, while at the same time reducing the usefulness of the device (see Rousselet, CF, A Description of the Rousselet Compressorium, JQMC vol IX, 1904-1906 p 137-8). This compressor differs from the original Rousselet Compressor, in that there is a continuous circle rather than part circle for the top plate. Another Watson change, not on this example, was to use screws to secure a brass plate to hold the upper glass in place. This change, which is not reflected in this example, was a distinct disadvantage over the method of gluing the top glass on forming a seal so that fluids or immersion oil would not seep under the top brass ring. The model shown in the engraving to the left from the 1912-13 Watson catalog, is not the same as the model shown above.