FIRST PERIOD.
THE DARK AGES.
More than three hundred years have elapsed since the influence and actinism of light on chloride of silver was observed by the alchemists of the sixteenth century. This discovery was unquestionably the first thing that suggested to the minds of succeeding chemists and men of science the possibility of obtaining pictures of solid bodies on a plane surface previously coated with a silver salt by means of the sun’s rays; but the alchemists were too much absorbed in their vain endeavours to convert the base metals into royal ones to seize the hint, and they lost the opportunity of turning the silver compounds with which they were acquainted into the mine of wealth it eventually became in the nineteenth century. Curiously enough, a mechanical invention of the same period was afterwards employed, with a very trifling modification, for the production of the earliest sun-pictures. This was the camera-obscura invented by Roger Bacon in 1297, and improved by a physician in Padua, Giovanni Baptista Porta, about 1500, and afterwards remodelled by Sir Isaac Newton.
Two more centuries passed away before another step was taken towards the revelation of the marvellous fact that Nature possessed within herself the power to delineate her own beauties, and, as has recently been proved, that the sun could depict his own terrible majesty with a rapidity and fidelity the hand of man could never attain. The second step towards this grand achievement of science was the construction of the double achromatic combination of lenses by J. Dolland. With single combinations of lenses, such pictures as we see of ourselves to-day, and such portraits of the sun as the astronomers obtained during the late total eclipse, could never have been produced. J. Dolland, the eminent optician, was born in London 1706, and died 1762; and had he not made that important improvement in the construction of lenses, the eminent photographic opticians of the present day might have lived and died unknown to wealth and fame.
The observations of the celebrated Swedish chemist, Scheele, formed the next interesting link between the simple and general blackening of a lump of chloride of silver, and the gradations of blackening which ultimately produced the photographic picture on a piece of paper possessing a prepared surface of nitrate of silver and chloride of sodium in combination. Scheele discovered in 1777 that the blackening of the silver compound was due to the reducing power of light, and that the black deposit was reduced silver; and it is precisely the same effect of the action of light upon chloride of silver passing through the various densities of the negative that produces the beautiful photographic prints with which we are all familiar at the present time. Scheele was also the first to discover and make known the fact that chloride of silver was blackened or reduced to various depths by the varying action of the prismatic colours. He fixed a glass prism in a window, allowed the refracted sunbeams to fall on a piece of paper strewn with luna cornua—fused chloride of silver—and saw that the violet ray was more active than any of the other colours. Anyone, with a piece of sensitised paper and a prism, or piece of a broken lustre, can repeat and see for themselves Scheele’s interesting discovery; and anyone that can draw a head or a flower may catch a sunbeam in a small magnifying glass, and make a drawing on sensitised paper with a pencil, as long as the sun is distant from the earth. It is the old story of Columbus and the egg—easy to do when you are shown or told how.
Charles William Scheele was born at Stralsund, Sweden, December 19th, 1742, and died at Koeping, on lake Moeler, May 21st, 1786. He was the real father of photography, for he produced the first photographic picture on record without camera and without lens, with the same chemical compound and the same beautiful and wonderful combination of natural colours which we now employ. Little did he dream what was to follow. But photography, like everything else in this world, is a process of evolution.
Senebier followed up Scheele’s experiments with the solar spectrum, and ascertained that chloride of silver was darkened by the violet ray in fifteen minutes, while the red rays were sluggish, and required twenty minutes to produce the same result.
John Wm. Ritter, born at Samitz, in Silesia, corroborated the experiments of Scheele, and discovered that chloride of silver was blackened beyond the spectrum on the violet side. He died in 1810; but he had observed what is now called the fluorescent rays of the spectrum—invisible rays which unquestionably exert themselves in the interests and practice of photography.