Sodium (11)
Hydrogen Lanthanum Titanium Silicon
Sodium Niobium Manganese Strontium
Nickel Palladium Chromium Barium
Magnesium Neodymium Cobalt Aluminum (4)
Cobalt Copper Carbon (200 or more) Cadmium
Silicon Zinc Vanadium Rhodium
Aluminum Cadmium Zirconium Erbium
Titanium Cerium Cerium Zinc
Chromium Glucinum Calcium (75 or more) Copper (2)
Manganese Germanium Scandium Silver (2)
Strontium Rhodium Neodymium Glucinum (2)
Vanadium Silver Lanthanum Germanium
Barium Tin Yttrium Tin
Carbon Lead Niobium Lead (1)
Scandium Erbium Molybdenum Potassium (1)
Yttrium Potassium Palladium

_Doubtful Elements_.

Iridium, osmium, platinum, ruthenium, tantalum, thorium, tungsten,
uranium.

_Not in Solar Spectrum_.

Antimony, arsenic, bismuth, boron, nitrogen, caesium, gold, indium,
mercury, phosphorus, rubidium, selenium, sulphur, thallium,
praseodymium.

With respect to these tables, Prof. Rowland adds: "The substances under
the head of 'Not in the Solar Spectrum' are often placed there because
the elements have few strong lines or none at all in the limit of the
solar spectrum when the arc spectrum, which I have used, is employed.
Thus, boron has only two strong lines at 2497. Again, the lines of
bismuth are all compound, and so too diffuse to appear in the solar
spectrum. Indeed, some good reason generally appears for their absence
from the solar spectrum. Of course, there is but little evidence of
their absence from the sun itself; were the whole earth heated to the
temperature of the sun, its spectrum would probably resemble that of the
sun very closely."

The powerful instrument used at Baltimore for photographing spectra, and
the measuring engine constructed to fit the photographs so that its
readings give the wave lengths of lines directly within 1/100 of a
division on Angstroem's scale, give the foregoing results a weight
superior to many others published.

* * * * *

ALLOTROPIC FORMS OF METALS.

Writing on some curious properties of metals and alloys, Mr. W.C.
Roberts-Austen, says the _Engineer_, remarks t