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MONTHLY MICROSCOPICAL JOURNAL, 



JANUARY 1, 1873. 



I. — A New Form of Micro-spectroscope. 

 By Edward J. Gayer, Surgeon H.M. Indian Army. > 

 {Read before the Koyal Microscopical Society, Dec. 4, 1872.) 

 Plate I. (Lower portion). 



In the form at present in use, the Sorby-Browning direct vision 

 micro-spectroscope, the divergent rays of light received from the 

 object-glass are collected at the eye end of the microscope by a 

 lens, placed about an inch in front of the slit, and after passing 

 through it, are rendered parallel in the usual way by an achromatic 

 collimating lens, before entering the compound direct-vision prism, 

 through which the spectrum is viewed directly without a telescope. 



In the new form, the divergent rays issuing from the object- 

 glass of the microscope are at once passed through the slit, placed 

 about an inch from the objective, without passing through any 

 collecting lens ; the prisms are not compound, and the spectrum is 

 looked at through a telescope. The advantages of the new form 

 are, that there is more light, more dispersive power, and that it is 

 quite possible even with high powers to use a telescope for magni- 

 fying the spectrum, and collecting the whole of the light passing 

 through the prisms ; also no special form of micrometer is necessary 

 because as there is a telescope any ordinary micrometer can be 

 brought to focus and rendered visible. A reference to the annexed 

 Plate will render the instrument more intelligible. 



A is the objective ; B, the arm of the stand of the microscope 

 carrying the body C ; t> is the slit of the spectroscope ; E, the 

 collimating lens ; F, F, two dense flint-glass prisms of 60°; (x, the 

 object-glass of the telescope ; I, one of the eye-pieces belonging to 

 the microscope ; H, rack- work motion to the eye-piece of the tele- 

 scope ; K, the usual apparatus for the second spectrum ; N, the 

 micrometer. There are screw adjustments in the brass plate and 

 tube in which the prisms are placed. 



To use this micro-spectroscope, the tube of the microscope should 



be unscrewed at L, and replaced by the spectroscope, which should 



uj be made to fit the same screw. The angle, which the telescope 



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