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. See Fixing 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. See Stops.
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. See Collodion 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, 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 (see Nitrite 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;
increases sensitiveness of Collodion plate, 92;
dissolves Iodide of Silver, 86;
discoloured by Albumen, 245, 329;
forms a compound with Honey, 289;
with various other organic bodies, 21;
very little acted on by Glycerine, 342;
mode of recovering the Silver from, 372.
Nitrate Bath, mode of preparing for glass Positives, 110, 203;
for Collodion Negatives, 116, 211;
its power of dissolving Iodide of Silver, its occasional acidity and alkalinity explained, 86;

the mode in which Acetate of Silver may be formed in it, 89;
a list of the substances by which it is decomposed, 90;
changes by use, 91;
effect of these changes on sensitiveness, 97;
on intensity, 102;
care required to prevent it from yielding foggy pictures, 104;
a caution against the too frequent addition of alkali, 204;
quantitative testing of the Bath, 371.
Nitrite of Silver, adds to rapidity of development, 102;
tends slightly to produce fogging, 104;
solarizes the high lights, 111.
Nitric Acid, its preparation and properties, 355;
its oxidizing powers, 12;
impairs sensitiveness of Collodion film, 93;
lessens rapidity of development, 98;
tends to prevent fogging, 104;
sometimes usefully employed for glass Positives, 110;
contra-indicated for Negatives, 116;
its accumulation in the Nitrate Bath explained, 94;
mode of removing it, 90;
cannot exist in contact with Acetate of Silver, 116;
produces stains on cloth, 215;
mode of determining the strength of Commercial Nitric Acid, 186;
table of strength of Nitric Acid of different densities, 378.
Nitro-Sulphuric Acid, explained, 77;
process for making by mixed acids, 186;
by Oil of Vitriol and Nitre, 190;
should not be used cold, 83.
Nomenclature, chemical, 315.
Norris, Dr., his dry Collodion process, 298.
Notation, chemical, 318.
Organic bodies, chemistry of, 324.
Oxide of Silver, preparation and properties, 17;
dissolves in the Nitrate Bath, rendering it alkaline, 88;
properties of its solution in Ammonia, 362;
preparation of ditto, 247;
its solution in Nitrate of Ammonia used in Photography, 249.
Oxymel, keeping process, 291;
preparation of Oxymel, 360.
Paper, Photographic, selection of, 240;
peculiarity of English papers, 241.
Paper, sensitive, for printing. See Sensitive Paper.
Perchloride of Iron, preparation of toning Bath with, 160.
Permanence of Positives, mode of testing, 169.
Photographic image, chemical composition of, 140;
action of destructive tests on, 145.
Photographic properties of Salts of Silver, 18;
of Iodide of Silver upon Collodion, 74.
Photographic researches by the Author, 140.
Photography, historical sketch of, 6;
the term explained, 61.
Portrait lenses, theory of their construction, 59;
rules for their use, 227;
mode of finding chemical focus, 229.
Portraits, drapery for, 66;
directions for taking, 220;
the position of the Camera, and other points of importance, 228;
the time of exposure, 221.
Positive printing, on Albuminized paper, formulÆ for, 241;
on plain paper, formulÆ for, 245;
on Ammonio-Nitrate paper, formula for, 246, 258;
by development, formulÆ for, 259;
manipulatory details of printing, fixing, toning, washing, and mounting, 251;
process of toning by Sel d'or, theory of, 134;
practice of, 267;
reasons for the want of correspondence between different formulÆ, 257;
use of Chloride of Gold in toning, 132, 271;
theory of the preparation of the sensitive paper for Positives, 122;
theory of the process of fixing, 129;
of toning by Gold, 132;
the Author's researches, 140;
rationale of the printing process, 120;
composition of the image, 140;
fading of Positive prints, 160;
destructive action of Sulphur on, 145;
of oxidizing agents on, 148;
of Chlorine, acids, boiling water, etc., on, 151;
of combustion of coal-gas on, 153;
effect of damp air on, 153;
theory of mode of washing Positives, 162;
comparative permanency of prints, 166;
mode of testing permanency, 169.
Positives, definition of, 106;
Collodion Positives, theory of production of, 108;
formulÆ for solutions for, 201;
development of, 111, 221;
Collodion and Nitrate Bath best adapted for, 109;
mode of whitening by Bichloride of Mercury, 112;
solution for whitening, 207;
mode of backing up, 226;
spots and markings on, 284;
mode of printing Positives on Collodion, 272.
Positives, enlarged, mode of printing, 272.
Practice of Collodion process, 183.
Preservative processes for Collodion plates, 289.
Printing, Photographic, theory of, 120;
practical details of, 240.
Prism, refraction of light by, 51;
diagram of formation of spectrum by, 47;
explained, 54.
Prismatic spectrum, 47, 61.
Protonitrate of Iron, preparation of, 206;
a feeble developer when free from excess of Sulphate of Iron, 98;
theory of its mode of action, and rules for its use, 112;
cannot be prepared in quantity by adding Nitrate of Potash to Sulphate of Iron, 314;
sometimes requires the addition of Nitrate of Silver, 206.
Protosulphate of Iron, its preparation and properties, 29;
its characteristics as a developer for Collodion Positives, 111;
not well adapted for developing Collodion Negatives, 117;
preparation of the solution for Positives, 205;
mode of applying it to the plate, 221;
to remove iron stains on glass, 215.
Pyrogallic Acid, its preparation and properties, 28;
solution for developing glass Positives, 205;
for Negatives, 211;
cannot be used without Acetic Acid, 105;
less adapted for developing paper pictures, 178;
requires addition of Nitric Acid when used for Positives, 111;
superior to Sulphate of Iron for developing Negatives, 117, 144;
mode of obviating the brown discoloration of developing solutions, 212.
Pyroxyline, its nature and properties, 75;
preparation of, by Mr. Hadow's formula, 186;
by a rule-of-thumb mixture of the acids, 188;
by the Oil of Vitriol and Nitre process, 190;
details of immersing, washing, and drying, 191;
the glutinous variety produced by cold acids, 83;
recapitulation of the effects of varying the strength of the acid mixture, 193;
spontaneous decomposition of Pyroxyline, 166.
Reduction of metallic oxides by developers, theory of, 26;
of Silver salts by developers, theory of, 30;
practical details of reducing Silver compounds to metallic state, 372.
Salts nature of, 310.
Salts of Silver, their preparation and properties, 12;
their Photographic action, 18;
theory of their reduction by developer, 30;
directions for obtaining metal from, 372.
Sel d'or, toning process by, its theory, 134;
its practical details, 267;
its advantages, 271;
gives permanent prints, 167.
Sensitiveness, term explained, 92;
conditions favourable to, 97.
Sensitiveness of Collodion film, causes influencing, 92;
superior sensitiveness partially explained, 74;
preservation of sensitive film, 288.
Sensitive paper, theory of preparation of, 22, 122;
its darkening by light described, 123;
preparation of Albuminized paper, 241;
of plain paper, 245;
of Ammonio-Nitrate paper, 246, 258;
of paper for Negative processes, 259;
causes which affect the sensitiveness of Positive paper, 123;
which alter the colour of the image, 126;
spots and markings on, 285;
a large excess of Nitrate of Silver essential, 124;
the paper should not be kept too long, 130, 286.
Serum of Milk, preparation of, 262, 355;
used in Negative printing process, 262.
Shadbolt, Mr., his Honey keeping process, 289;
employs artificial light in Micro-Photography, 237.
Silver, properties of, 362;
estimation of, in Nitrate Baths, 371;
recovery from waste solutions, 372;
reduction from Chloride, 374;
stains, removal of, 377.
Size, mode of removing, from paper Positives, 255.
Solar spectrum, 47, 61.
Soluble paper. See Pyroxyline.
Specific gravity of liquids, mode of finding, 375.
Spherical aberration, 56.
Spirits of Wine, preparation and properties, 330;
not always sufficiently strong for Collodion, 84;
mode of rectifying, 196;
sometimes contaminated with, fusel oil, 96.
Spots on Collodion plates, 279;
on paper Positives, 285;
on prints obtained by development, 266;
on preserved Collodion plates, 293.
Stains, Silver, removal of, 377.
Stereoscope, invention of, 67;
theory of, 68;
Wheatstone's, 69;
Brewster's, 70.
Stereoscopic Photographs, rules for taking, 71;
practical details of, 232.
Stops, theory of use of, 57;
simple mode of making, 228;
position of the stop often important, 230.
Strength of acids, tables of, 378.
Subchloride of Silver, its preparation and properties, 15;
decomposed by fixing agents, 141.
Suboxide of Silver, its properties, 18;
forms compounds with organic matters. Citric Acid, Albumen, etc., 21.
Substitution, laws of, explained, 78.
Sulphate of Iron. See Protosulphate of Iron.
Sulphate of Quinine, absorption of chemical rays by, 65.
Sulphuric Acid, table of strength of, 378.
Sutton, Mr., theory of Sel d'or toning process, 134;
practical details of, 267;
Negative printing process, 262;
preparation of Serum of Milk for, 355.
Symbols, use of, 318.
Syruped Collodion film, 289.
Talbot, Mr., his discoveries, 9;
theory of Calotype process, 176.
Taupenot, M., his Collodio-Albumen process, 181;
practical details of, 294.
Temperature, its effect upon development of Collodion film, 102;
upon fogging, 105;
upon keeping Collodion, 210;
upon action of fixing Bath for paper Positives, 130;
upon Hypo toning Bath, 136.
Test-papers, use of, 376.
Toning Bath for Positives, with Sel d'or, 134, 267;
with Hyposulphite and Gold, see Fixing and Toning Bath;
with Chloride of Iron and Hyposulphite, 160.
Toning of Positives, term defined, 121;
may injure the stability of the proof, 154;
points to be kept in view to avoid fading, 167;
manipulatory details of, 253;
by Sel d'or, 267.
Transparencies, mode of printing, 273.
Varnishes for Collodion Photographs, 226.
View Lenses, directions for using, 230.
Vocabulary of Photographic chemicals, 327.
Washing Positive prints, rules for, 162;
details of, 255.
Waxed paper process, theory of, 178.
Weights and Measures, table of,

PRINTED BY JOHN EDWARD TAYLOR, LITTLE QUEEN STREET, LINCOLN'S INN FIELDS.