Pee ted). a! 
Soren 
Le. ae Langley— Determination of Wave-lengths 
g ere 
reason, I believe, to hope that the labors of Professor Rowland . 
spectrum to the normal one. The reason why this, 0 = 
able information, has never been obtained before, 18 t o-fo ae 
Ww 
(1st.) While the measurement in question can best be mace 
