Chemistry and Physics. 163 
side or the other of a figure on the e expressing a wave 
length ;” p. 259, line 18, one iron line “ ery eleven wave 
lengths was used ;” 261, line 18, no element gives “a lin 
each wave length being five millimeters in extent ;” and p. 30, 
line 28, “in the eighteen wave lengths represented in the dia- 
gram.” There are eighteen scale divisions in the diagram, each 
dredths of a scale division, not of a wave ength. From the fact 
preparation of his solar photographs to use reflected rays exclu- 
Sively ; saying, pie t line, “ at no time did the solar rays 
pass through glass ; all error that might arise d efraction 
ise durin 
was thus avoided.” After this virtual condemnation of the use of 
Ing, constructing even his chart upon them as a basis, p. 258, line 
“ce th 
sun spectrum were to be established, was photographed with 
glass prisms and achromatic lenses. : : 
hird, the author states that the prisms with which the 
Spectrum of oxygen was photographed were adjusted “to the 
minimum deviation of D’.” Supposing D, to be meant, this 
