Chapter III: ELECTRICITY, LIGHT, HEAT, ETC.--Spectrum Gratings 5822

A New Pocket Opera Glass.--4 figures 5822

Atoms, Molecules, and Ether Waves. By JOHN TYNDALL.
Action of heat and light on molecules.--Heat as an
agent in exploring molecular conditions.--The results
of a recent incursion into the extra-sensible world
of atoms and molecules 5823

Apparatus for Measuring Electricity at the Upper
School of Telegraphy. By E. MERCADIER.--5 figures.
Constant vibrator.--The Electrical tuning fork.
Arrangement for testing electric piles.--Very rapid
electric tuning fork.--A vibrating micrometer 5824