CHAPTER VIII.. Actinism--Chemical Radiations.

ACTINISM--CHEMICAL RADIATIONS.

The Sun-ray and its Powers--Darkening of Horn Silver--Niepce’s Discovery--Prismatic Spectrum--Refrangibility of Light, Heat, and Actinism--Daguerre’s Discovery--Photography--Chemical Effects produced by Solar Radiations--Absorption of Actinism--Phenomena of the Daguerreotype--Chemical Change produced upon all Bodies--Power of Matter to restore its Condition--Light protects from Chemical Change--Photographs taken in Darkness--Chemical Effects of Light on organized Forms--Chemical Effects of Solar Heat--Influence of Actinism on Electricity--Radiations in Darkness--Moser’s Discoveries, &c. 166