414 



Prof. Henry A. Rowland o>i Gratings 









: £ 



: © 



Ha* 



: : 8 



:::::::::::: : : p 



hf 



i—i 

 :::::::::::: : : p 



i-T 



:.: = ■.:■:•=■::::: : % 1 



c 



:::::::::::: : 



CO T-H 



8 § 



a 

 Hi 





2 £ 

 © 9 





X 



Ha 



CO 



O ^H 



o o 

 © ^ 





*- 



CO t- 



::::::::::: o i— i 

 ::::::::::. p p 



CO t^ 



© -+ 



T 1 © 



1-3° 



(M (M t- rH 



:::::::::©©t-h o 



5 ? 



hT 



<M CO 00 00 rH 



:::::::: © ^ *-< © co 



:::::::.pppp i-h 



CO o 



© © 



•<* 

 Ha 



-H CO b- O O CO 00 



: : : : ; : © © t-h o t- o cm 



T-H 00 

 T-H T^ 



© © 



hT 



t- © ir; O O CO CO 



: : : : : ; - -* c. j> x w ~h • 

 : o o o --I r-i — i ©3 



• °0 



O CO 

 00 o 



p p 



l"3 



N O (M ^ a © N :j W © © 



: : :oo^h<moocooco© . 10 ess 



.OOOi-«i-l<MrHi-i© gOO 



=« 



CO lO 



t-H . O 



° JH ° 





©COO"l©THCO©UO©Thfc-©*~© 



: h eo oo w is w to h o © -o «-i t- o 

 :ooor-iT-ico<Mi-iooi-iT-i©o 



Li lO (M 



iS £r © 



© © o 





o 



OONC-lOSOOOOONOOrtOiMO 

 OCOOlCO^OOiOO^OOCOOC^O 



© © o 



(MOO 

 © © © 



^ 



— 1 o 



k 



»Q <M © © 



O CO <M t-h 



o<M^pooppopopoo»90o 



O 

 © o © 



00 00 © 



T— I 



