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SUMMARY OF CURRENT RESEARCHES RELATING TO 



Watson and Sons' Incandescent Gas Lamp.* — This lamp is shown 

 in fig. 11. It has an incandescent burner, with by-pass, mica chimney, 

 and metal hood. An iris diaphragm may be fitted in the hood, so that 

 the diaphragm aperture may be used as the light-source, and the mantle 

 structure eliminated. 



Fig. 11. 



Dr. 6. Johnstone Stoney's Improved Heliostat.f — Messrs. Watson 

 have constructed this instrument (fig. 12) under the designer's super- 



Fig. 12. 



vision, and the ^improvements effected in it render it more than ever 

 suited to the requirements of the physicist and photomicrographer. It 



* W. Watson & Sons' Catalogue, 1902-3, p. 116. f Tom - cit -> P- 106. 



