110 Mr. Loyd A. Jones on a Method and Instrument 

 Case II., ^ <k, 



-D2 



leads to family of straight lines all passing through the point 

 # = 0, y=— 51, the slope of any one being given by the 

 equation 



tana= W(*-l)- 



Fig. 4.' 













v-y< 



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/ 





/ 





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i 





/ 





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i 





f 











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V X 



hS 







■^y 







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If \ 



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io 























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1 ^>^ 

















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• REFLECTION • FACJOIU Ra> ■ 

 Visibility as a Function of the Reflexion Factor. 



It will be noticed in solving for the value of tan a that in 



Case I., where ■— >Jc, 



the value is negative, while the value of tan a in Case II. is 

 positive. This offers a convenient method for indicating 



