"
Furthermore, from a comparison of the dispersive and refractive powers
of these glasses, as given in the list, I find that objectives
constructed from them will leave so great aberrations of higher order,
both spherical and chromatic, that the gain by the reduction of the
secondary spectrum would be greatly overbalanced.
In conclusion, I wish to say that while I would beware of
underestimating the great scientific and practical value of the
endeavor of the new German glass makers to produce improved optical
glass, and the great benefit accruing to opticians and all others
interested in the use of optical instruments, I think it wise not to
overestimate the real value of the defects of the common crown and
flint glass, which I have sought to explain in this paper. And, for
myself, I prefer to fight the more serious defects first, and when its
time has come I will see what can be done with the secondary spectrum.
* * * * *
PROBABLE ISOLATION OF FLUORINE. DECOMPOSITION OF HYDROFLUORIC ACID
BY AN ELECTRIC CURRENT.
By M.H. MOISSAN.
In a former memoir[1] we showed that it was possible to decompose
anhydrous hydrofluoric acid by the action of an electric current. At
the negative pole hydrogen collects; at the positive pole a gaseous
body is disengaged, having novel properties.
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