Ch. VIII] MICRO-SPECTROSCOPE 247 



spectrum (absorption bands). These absorption bands could be 

 seen and their significance appreciated by a person wholly color blind 

 — and there is occasionally such a person. 



§ 392. A micro-spectroscope, spectroscopic or spectral ocular, is 

 a direct-vision spectroscope in connection with a microscope ocular. 

 It consists of a direct-vision spectroscope prism of the Amici pattern, 

 and of considerable dispersion, placed over the ocular of the microscope. 



^2^ 



k0.7i. 



Visible 

 Radiation 

 Ultra-Violet Infra-Red 



Fig. 144. Normal Spectrum Showing Visible and Invisible Radiation. 



(Magnified 20,000 times vertically and 50,000 times horizontally). 

 (From Optic Projection). 



As shown in white, the useful radiation for vision lies between Xo.4;U and 

 Xo.7/i. Under favorable conditions the eye can see shorter and longer radia- 

 tions. 



Ultra-nolet Radiation having waves shorter than Xo.4yu; (Black). 



Infra-red Radiation with waves longer than \o.yiJ,. Radiation up to a 

 wave length of X2yLi is here shown in black. 



This direct vision or Amici prism consists of a single triangular 

 prism of heavy flint glass in the middle and one of crown glass on 

 each side, the edges of the crown glass prisms pointing toward the 

 base of the flint glass prism, i.e., the edges of the crown and flint 

 glass prisms point in opposite directions. The flint glass prism serves 

 to give the dispersion or separation into colors, while the crown-glass 

 prisms serve to make the emergent rays approximately parallel with 

 the incident rays, so that one looks directly "into the prism along 

 the axis of the microscope. 



