... constructed; to the second we are indebted for the power of the lenses, and the blessings of sight, for the light acts upon the retina of the eye in the samemanner as on the lens of a camera. The latter ... the cross bar g, and fits the pot so accurately that iteffectually prevents the escape of the vapor of the iodine, bromine or other accelerating liquid containedtherein. The other half of the ... plainlypercieved the effect, in the gradual darkening of various parts of the view, which was the old stone fort in the rear of the school garden, with the trees, fence, &c. I then became convinced of the...