352 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



of the objective, so as to cut off eacli alternate one of the upper row of 

 spectra in Fig. 93, that row will obviously become identical with the 

 lower one, and if the theory holds good, we should find the image 

 of the upper lines identical with that of the lower. On replacing 



Fig. 97. 



Fig. 98. 



the eye-piece we see that it is so, the upper set of lines are doubled 

 in number, a new line appearing in the centre of the space between 

 each of the old (upper) ones, and upper and lower set having become 

 to all appearance identical (Fig. 98). 



Fig. 99. 



Fig. 100. 



In the same way, if we stop oflF all but the outer spectra as in 

 Fig. 99, the lines are apparently again doubled, and are seen as in 

 Fig. 100. 



Fig. 101. 



Fig. 102. 



K 



A case of apparent creation of structure similar in principle to the 

 foregoing, though more striking, is afforded by a network of squares 

 such as Fig. 101, having sides parallel to this page, which gives the 

 spectra shown in Fig. 102, consisting of vertical rows for the hori- 

 zontal lines and horizontal rows for the vertical ones. But it is 

 readily seen that two diagonal rows of spectra exist at right angles 



