the Echelon Spectroscope. 



m 



intensity of the lines, and increase the distance between two 

 successive orders, while a slight tilt in the other direction will 

 have very little effect either on the intensity of the lines or on 

 the dispersion of the orders. The explanation of this effect is 

 at once seen when we consider the effect of tilting the 

 instrument. 



Fiff.4. 



DIRECTION 



VF L/GHT 



D/RECT/OM Of/NC/D. EIGHT 



i 



{ ' ' Scale = Full Size 



In position 1 (fig. 4) the steps overhang each other, as 

 were, and their effective width is rapidly diminished. 



