Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . s told by thegenii that a certain subtle ingredient spread upon canvas would secure imagesfrom Nature cast thereon and fix them. He was either too frivolous, or toosecretive to reveal more, and again the lasso failed. In 1777, Scheele, the famous chemist of Sweden, discovered that chloride ofsilver was much more sensitive to the rays of blue and violet in ligiit than itwas to those of red and green. 3. In 1780, Prof. Charles, in a course of lectures, by means of
Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . s told by thegenii that a certain subtle ingredient spread upon canvas would secure imagesfrom Nature cast thereon and fix them. He was either too frivolous, or toosecretive to reveal more, and again the lasso failed. In 1777, Scheele, the famous chemist of Sweden, discovered that chloride ofsilver was much more sensitive to the rays of blue and violet in ligiit than itwas to those of red and green. 3. In 1780, Prof. Charles, in a course of lectures, by means of a strongsolar ray projected a shadow of the head of one of his pupils upon a sheet ofwhite paper which had been soakedin a solution of chloride of silver, andsecured a silhouette in white on a blackground—but it fled on exposure to thelight. Wedgewood and Sir HumphreyDavy made similar experiments, andin 1802 published a remarkable treat-ise on the reproduction of objects bylight. James Watt, the inventor of thesteam-engine, also interested himselfin this research; but for none of the would the captured imagery remaii Fig. distinguished scientistssun, its creator. when facing the 3. Porta lost no time in recommending the use of the chirk-room to all ])aintersdesirous of obtaining exact and minute delineation; and, shortly afterward, Canalettoprofited by his advice, and employed the invention for taking his admirable views ofVenice. What would the Neapolitan philosopher and the Venetian painter have said had theybeen told that this image of the dark-room would one day draw itself, not merely fugi-tively, but that it would print itself on a glass moistened with chemical agents? that itwould transform itself into a durable picture, only to be compared for exactness to thereflection of a mirror? This wonder was, indeed, to be accomplished unknown to Porta;but his work was not in itself sufficient to conduct science to such a result; numerouslaborers had also to add their ston
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