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SUMMARY OF CURRENT RESEARCHES RELATING TO 



MICROSCOPY. 



A. Instruments, Accessories, &c.* 

 (31 Illuminating- and other Apparatus. 



Beck-Thorp Diffraction Spectroscopes. f — This series of spectroscopes 

 is claimed to be the first serious attempt to apply the advantages of the 

 diffraction grating to the whole fiel(t of spectroscopic research. The list 

 includes small instruments to be carried in the pocket of those interested 

 in colour-printing or in chemical or colour industry, as well as more perfect 

 instruments with scales of measurement. These latter include a chemical 

 spectroscope of great dispersion, a sun prominence spectroscope, and a 

 wave-length spectroscope for determining the wave-length of light with 

 great accuracy. Of these we give the following examples. 



The Beck-Thorp "Minimum" Pocket Diffraction Spectroscope 

 (fig. 51) gives a dispersion of about 20° or about double that of the 



ordinary direct-vision prismatic instrument. It will readily show the 

 more prominent Fraunhofer lines, and the rainband lines distinctly. 



The Beck-Thorp " Regular " Pocket Diffraction Spectroscope (fig. 52) 

 has a dispersion of about 'M)° and shows hundreds of lines in the solar 



spectrum, the D line being well separated. It has an adjustable plati- 

 noid slit and a sliding focusing adjustment. 



The Beck-Thorp Patent Reading Pocket Diffraction Spectroscope 

 (fig. 5;^)) has the same optical qualities as the foregoing but also an 

 important addition. On looking through the instrument will be seen 

 the spectrum and above it an illuminated arrowpoint. A graduated 

 milled head moves this point along the spectrum and the position of 



• This subdivision contains (1) Stands ; (2) Eye-pieces and Objectives ; (3) 

 Illuminating and other Apparatus ; (4) Photomicrography ; (5) jNIicroscopical 

 Optics and jManipulation ; (G) JNIiscellaueous. 



t R. and J. Beck's Special Catalogue (1907) 8 pp. (9 figs.). 



