Aberration, chromatic,54;spherical,56.Accelerating agents, their mode of action in Collodion explained,95.Acetate of Silver, its preparation and formula,365;its formation in Nitrate Bath explained,89;ensures absence of free Nitric Acid,116;tends slightly to favour fogging and spots,104;contra-indicated for glass Positives,111.Acetic Acid, properties and mode of testing purity of,327;useful in preventing fogging,104;in rendering the development slow and even,99;does not coagulate Albumen,329;a good commercial form of acid,212;Acetic Acid essential in Calotype, waxed paper, and Albumen processes,177;also in printing paper Positives by development,260.Aceto-Nitrate of Silver, term explained,177.Achromatic Lenses, their construction explained,55;the visual and chemical foci often coincident in,60.Acids, nature of,308.Actinism, explained,61;importance of distinguishing Actinic from visual rays,62;mode of finding Actinic focus,229.Affinity, chemical,312.Albumen, its chemistry,328;forms a compound with oxide of Silver,20;used in Positive printing to produce a fine surface layer,122;to increase sensitiveness,125;affects the colour of the prints,127;protects the image from oxidation,150;putrifies when exposed to moisture,155;discolours the Nitrate Bath,245.Albumen negative process, its invention,10;theory of,180;Collodio-Albumen process of M. Taupenot,294.Albuminized paper, formula for,241;slow in fixing,131;not well adapted for toning by Sel d'or,269;good for stereoscopic subjects and small portraits,249;cannot be sensitized with Ammonio-Nitrate of Silver,246.Alcohol, its chemistry,330;sometimes too dilute for making Collodion,84;mode of rectifying,196;must not contain impurities,96;effects of adding to Collodion,84,96;to developer,205.Alkalies, nature of,308.Alkalinity of Nitrate Bath, explained,88;the evils it produces,104;how to test for it,377;how to remove it,277.Amber varnish,226.Ammonia, preparation and properties,331;its use in fixing,42;Mr. Shadbolt's formula for,271;its action upon Chloride of Gold,343;effect of concentrated Ammonia upon Oxide of Silver,362.Ammonio-Nitrate of Silver, its chemistry,262;used in Positive printing to increase sensitiveness,125;to give black tones,127;cannot be used with Albumen,246;increases permanency of print,169;old Nitrate Baths not easily convertible into Ammonio-Nitrate,248;mode of preparing,247;best applied to the paper by brush or rod,248;Oxide of Silver in Nitrate of Ammonia, a useful substitute for it,249.Ammonio-Nitrate paper, formula for,246;a more simple formula, but less sensitive than the last,258.Atomic theory explained,322.Bath for fixing and toning Positives.SeeFixing and toning Bath.Bichloride of Mercury, whitening action on glass Positives explained,113;solution for,207;used to intensify Negatives,118;bleaches paper prints,151;should not be added to paste used in mounting prints,164;removes Silver stains,377.Binocular vision, phenomena of, explained,66.Blackening Negatives,37,117.Black tones, mode of obtaining, in paper Positives,168,246.Bromide of Silver, its preparation and properties,17;its superior sensibility to coloured light,63;less acted on by white light than Chloride,19;less sensitive to invisible image than Iodide,25;employment in Collodion,101;found useful in Photographing by artificial light,66;diagram of chemical spectrum on,64.Bromo-Iodide of Silver,173.Brushes, mode of applying Silver solutions by,248.Calotype process, theory of,176.Camera, its first invention,7;theory of its construction,54;mode of testing accuracy of,229;cause of the image being inverted,53;the term "flatness of field" explained,54;best position of the Camera for portraits,220;for architectural subjects,231;a funnel-shaped tube placed in front of the lens,229;stereoscopic Camera,234;microscope Camera,236.Causes of failure in Collodion process,276.Chemical affinity, illustrations of,312.Chemical elements,306.Chemical focus, directions for finding,229;shorter than visual in non achromatic lenses,60;longer than visual in microscopic objectives,237;varies slightly with the nature of the light,238.Chemical spectrum,61.Chemicals, Photographic, Vocabulary of,327.Chloride of Silver, its preparation and properties,14;more sensitive to white light than Bromide or Iodide,19;less sensitive to invisible image,24;its blackening by light explained,20,141;accelerated by excess of Nitrate,19;by organic matter,20,142;experiments illustrating darkening of papers prepared with,21;simple explanation of the mode of preparing sensitive papers with,22;agents which dissolve it,42;mode of reducing it to metallic state. 374.Chloride of Gold, its preparation and properties,342;action of Ammonia upon it,343;use of an alkaline solution of, for toning,132,271;compounds formed on adding it to Hyposulphite of Soda,133;mode of preparing the fixing and toning Bath with,250;the Sel d'or Bath with,267.Chromatic aberration,54.Citric Acid, forms a red compound with Suboxide of Silver,21,338;used in printing to give purple tones,128;formula for preparing paper with,246.Cleaning glass plates, theory of,39;details of,213.Collodion, its discovery,10;chemistry of Pyroxyline,75;physical effect of Ether and Alcohol in,83;of water in,85;glutinosity of,83;coloration of iodized, explained,85;sensitiveness and intensity affected by the change,97,99;details of manufacture of Collodion,185;Positive Collodion, theory of,108;formula for,201;Negative Collodion, theory of,113;formula for,208;Collodion for copying engravings,231;for keeping processes,298;for hot climates,210;for working by artificial light,238;to remove the brown colour from Collodion,86.Collodion film, the proper time for immersing it in the Bath,219;a thin film often good for direct Positives,109;a thicker film for Negatives,113;cause of the film falling away from the glass,83,293;spots and markings on,281;conditions which affect its sensitiveness to light,92;causes influencing its behaviour with the developer,98;mode of preserving sensitiveness of film,289.Collodio-Albumen process, theory of,181;practical details of,294.Colours, their nature explained,47;their chemical action on sensitive film,64;their photographic action assisted by reflection of white light,66.Combination, laws of,307.Conjugate foci, explained,52,272.Crookes, Mr., remarks upon chemical spectrum,63;upon waxed paper process,180;preservative process for Collodion films,289.Curvature of luminous image formed by lens, explained,53.Cyanide of Potassium, its fixing action explained,44;preparation of solution of,207;used to remove stains,377.Daguerreotype, its invention,8;theory of the process,171.Development of invisible image, explanation of,34-40;second, or intensifying stage explained,37;details of developing glass Positives and Negatives,221-223;development of paper Positives,259;conditions which increase or diminish rapidity of development,98;irregularities of development,103.Developers, their preparation and properties,26;comparative strength of,98;theory of, for Positives,111;for Negatives,117;formulæ for Positive developers,205;for Negative,211.Diagrams, mode of copying,232.Diaphragms for lenses.SeeStops.Double decomposition, illustrated,14;explained,314.Dry Collodion process,298.Elementary bodies, table of,306;combination of,307.Engravings, mode of copying,231;often yield dark-coloured prints,255.Equivalent proportions,320.Ether, properties of,339;purification of, for Photography,195;must be kept in a dark place,196;should not be distilled from residues of old Collodion,96.Experiments, illustrating action of Light upon Chloride of Silver,21;illustrating formation and development of invisible images,25;illustrating photographic action of coloured light,62.Exposure in the Camera, rules for Positives,221;for Negatives,225;for preserved Collodion plates,292;for microscopic photographs,238;effects of under and over-exposing,35;exposure required in Calotype process,177;in waxed paper,180;in Albumen negative process,181;in dry Collodion process,301;in Taupenot's process,297.Fading of Positives, explained at length,160;Author's researches on,153.Film, sensitive.SeeCollodion film.Filters, mode of cutting,376.Fixing, theory of,41;of paper prints explained,128;solution for fixing glass Positives and Negatives,212;manipulatory details of fixing,225;fixing paper Positives with Ammonia,271.Fixing and toning Bath, its preparation,250;conditions which favour or retard its action,135;certain states of the Bath injurious to the proofs,136;importance of keeping it in an active condition,168;must not be employed immediately after mixing,251;must not be allowed to become acid by constant use,168;theory of the gradual change of properties it undergoes,156.Foci, actinic and luminous,60;actinic, mode of finding,229;variation between them in microscopic objectives,237.Focussing the object,220.Fogging, theory of,103;mode of detecting causes of,276.Formulæ for solutions required in Collodion process,201;for papers used in Positive printing,241;want of correspondence between,257.Gallic Acid, its preparation and properties,27;used in paper processes,178;becomes mouldy by keeping,261.formula for developing paper Positives with,261.Gallo-Nitrate of Silver,177;discolours rapidly when developing dishes are not clean,179.Gelatine, its properties,341;forms a compound with an Oxide of Silver,21;employed in dry Collodion process,299;modified form of,302;affects the colour in printing processes,128;used in Positive printing to form an even surface layer,126;as a cement to mount Photographs,257.Glass plates, rules for cleaning,39;details of cleaning,213;mode of coating with Collodion,215;with Albumen,180.Glutinous Collodion, explained,83.Glycyrrhizine, its nature,342;its action in Collodion,114;formula for solution of,209.Gold, Chloride of.SeeChloride of Gold.Gold salts, their use in Photographic printing explained,131;in the Daguerreotype process,175.Gradation of tone, in Collodion Photographs, affected by the density of the film,109,113;by use of Glycyrrhizine,115.Gradation of tone, in paper Positives, conditions affecting it in prints obtained by direct exposure,123;in Positives printed by development,266.Hadow, Mr., researches on Collodion,77;formula for making Pyroxyline,187.Heliography, invented by M. Niépce,7.Historical sketch of Photography,6.Honey keeping process,289.Hunt, Mr., introduces Protosalts of Iron in developing,111.Hypo Bath.SeeFixing and Toning Bath.Hyposulphite of Silver, its peculiar changes in colour,129;the sweet compound which it forms with Hyposulphite of Soda,44.Hyposulphite of Soda, preparation and properties,43;theory of its fixing action,43;blackens Nitrate of Silver,129;causes a milkiness with acids,137;its decomposition by constant use in fixing,138;the salts it forms with Chloride of Gold,133;its conversion into sulphuretting Tetrathionate by Iodine and Perchloride of Iron,139;test for presence of,169.Iceland moss, its use in Positive printing,128;formula for preparing paper with,245.Imperfections in Collodion Negatives,282;in Positives,284;in paper Positives,285.Intensity, explanation of term,92;mode of increasing in Negatives,99, 114;effect of Acetate of Silver upon,116;of Nitrite of Silver upon,102;mode of diminishing, in glass Positives,109,110;conditions affecting intensity in paper Positives,123;in developed paper Positives,266.Invisible images, theory of formation of,34;development of,36;experiments illustrating,25.Iodate, how formed in Collodion film,94;produces insensitiveness,198.Iodide of Ammonium, preparation of,198;not fitted for iodizing Collodion required to be kept long,210.Iodide of Iron, an accelerator to Collodion,116.Iodide of Potassium and Silver, properties of,42;mode of iodizing Calotype papers by,177.Iodide of Potassium, tests of purity of,197;extent of solubility in Alcohol,351;dissolves Iodide of Silver,42.Iodide of Silver, its preparation and properties,16;unaffected by direct action of light,19;highly sensitive to invisible image,24;hypothesis of formation of latent image on,34;possibility of its reduction by Pyrogallic Acid shown,33;excess of Nitrate of Silver essential to its blackening by developer,36;diagrams of chemical spectrum on,61,64;fixing agents for,42;its solubility in the Nitrate Bath,86;retards the action of Hypo fixing and toning Bath,136;superior permanency of developed prints on,167;details of Negative printing process on,263.Iodine, in Collodion, diminishes sensitiveness,94;forms Nitric Acid and Iodate in the Bath,94;often useful in Positive Collodion,110;in Negative Collodion, if fogging occurs,105;mode of removing from Collodion,86.Iodized Collodion. See Collodion.Kaolin, properties of,335;used to decolorize Nitrate Baths,91;importance of purifying it before use,245.Landscape Photography, with preserved Collodion plates,288.Latent image. See Invisible image.Laws of substitution explained,78.Le Grey, M,, his toning process with Chloride of Gold,132;his waxed paper Negative process,178.Lenses, various forms of,51;foci of,52;formation of images by,53;use of stops,58;portrait,59;chemical foci of,60;chromatic aberration of,54;spherical aberration of,56;simple directions for using lenses,227;for finding chemical focus,229.Light; its action upon Silver Salts,19;experiments illustrating,21;formation of invisible images by,24;its alternating action upon Daguerreotype plate,39;its compound nature,46;photographic action of coloured light,60;refraction of light,49.Llewellyn, Mr., his Oxymel process,291.Manipulations of Collodion process,213;of Photographic printing,251;of toning by Sel d'or,267.Manuscripts, mode of copying,231.Markings on Collodion Pictures,281.Measures and Weights,379.Microscopic Photography,235.Moser, M. Ludwig, his researches on the development of invisible images,37.Mounting Positive Prints, substances which should be avoided in,155,164;details of,257.Negative processes for printing Positives,259,263.Negatives, definition of,106;Collodion Negatives, theory of production of,113;Calotype,176;waxed paper,178;Albumen,180;Collodio-Albumen (Taupenot),181;mode of developing Collodion Negatives,37,117,223;of converting Positives into,117;formula for solutions for Negatives,208;the Collodion best adapted for Negatives,114;spots and markings upon Negatives,282;decomposition of Pyroxyline a cause of fading of,166.Nitrate of Silver, preparation and properties of,12;preparation of from standard coin of realm,362;often contains free Nitric Acid,13;when very strongly fused, contains Nitrite (seeNitrite of Silver),14;not acted on by light,18;its reduction by Pyrogallic Acid explained,31;the melted Nitrate more certain in its action,13,101;its presence essential in developing the image,36,98;