W. Harkness—Color Correction of Achromatic Telescopes. 109 
During the entire progress of the storm of January 14-17, 
1877, the winds on Mt. Washington blew uninterruptedly from 
the northwest, and the least velocity reported was thirty-six 
miles per hour, showing that the movements represented on 
Plate IV were confined to the lower stratum of the atmosphere 
and did not reach to the height of 6,000 feet. 
Most of the cases enumerated in the table on page 103 agree 
with No. 81 in several of the particulars here stated. eir 
rapid movement eastward appears to have been due to an un- 
usual extension of easterly winds which seem to have owed 
their origin to the accidental proximity of areas of high barom- 
eter, and the influence of this high barometer was sustained by 
the precipitation of vapor which extended to an unusual dis- 
tance on the east side of the low center. 
Art. XIT1.—On the Color Correction of Achromatic Telescopes ; 
A reply to Prof. Cuas. S. Hasrrnes; by WM. Harkness. 
In the December number of this Journal, pages 434 , 
en distinguished Associate Professor of Physics of the Johns 
p : ‘ he 
i +A,, but that asserts nothing as to likeness of the latter 
Symbols in sign. (II) Thus in equation (16) may be negative 
