Chapter IV: ELECTRICITY, PHYSICS, ETC.--On the Theory of the

Electro-magnetic Telephone Transmitter.--By E. MERCADIER.

On the Theory of the Receiver of the Electro-magnetic
Telephone.--By E. MERCADIER.

Frew's Improved Pyrometer.--With engraving.

Dew.--Abstract of a paper read before the Royal Society of
Edinburgh.--By Mr. AITKEN.--Source of dew.--Observations of the
temperature of the ground.--Experiments.--Effects of
wind.--Excretion of drops of liquid by plants.--Radiating power of
different surfaces at night.