G. F. Becker—Correction for Vacuum in Chemical Analysis, 265 
photographing solar spectra, and thereby avoiding certain errors, 
and the employment of the silvered surface itself of a glass 
grating. 
2. The extension of the measurement of oxygen lines into 
the ultra-violet region. 
. The measurement in the region of less refrangibility than 
H, of lines of oxygen not heretofore recorded, and the use of 
projection as a method of measurement. 
4 establishment of a close relationship in position 
between certain lines in the solar spectrum and the lines of 
oxygen ; the slight differences that exist being assignable to the 
experimental difficulties in the way of making accurate meas- 
ures of the oxygen lines, and falling within the limits of error 
of experiment. 
5. The evolution of the fact that the lines of the solar spec- 
trum which appear to correspond to the lines of oxygen are 
weak, or faint, and show that that gas possesses a feeble absorb- 
ent power when compared with metallic vapors or gases like 
» He, Ca. 
_ 6. The demonstration that in Angstrém’s chart there are man‘ 
lines not assignable to any elementary body, and that these 
lines occupy very closely the positions of certain oxygen lines. 
7. The suggestion that the proof of the presence in the solar 
envelopes of oxygen, and other substances giving faint lines, 
1s a problem not to be solved by the comparison of two spectra 
of small dispersion. The solar spectrum in certain parts is so 
crowded with lines presenting all kinds of details, that the only 
Satisfactory way is to make measures of the positions of these 
'nes on a large scale, and as truly as possible, and then com- 
pare with these the most accurate measures of oxygen lines that 
can 
Art. XXTX.— Correction for Vacuum in Chemical Analysis ; 
by G. F. BecKrr. 
Turner, in his atomic weight determinations (1829) was, so 
_ 48 my information goes, the first to correct the apparent 
Weight of solid bodies in chemical analysis for the air displaced. 
Berzelius at first accepted this correction but afterward rejected 
it as insignificant. Erdmann and Marchand adopted the some- 
what illogical practice of reducing the body weighed to vacuum 
while neglecting the correction for the weights. Nor has the 
practice of living chemists in accurate investigations been less 
Contradictory. Some of them have entirely ignored the buoy- 
