the history and practice of the art of photography-第24章

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　in　one　of　his　memoirs　on　the　subject　from　which　I　again　copy　it。〃

〃A　paper　prepared　with　muriate　of　barytes　and　nitrate　of　silver；　allowed　to　darken　whilst　wet　in　the　sunshine　to　a　chocolate　color；　was　placed　under　a　frame　containing　a　red；　a　yellow；　a　green；　and　a　blue　glass。　After　a　week's　exposure　to　diffused　light；　it　became　red　under　the　red　glass；　a　dirty　yellow　under　the　yellow　glass；　a　dark　green　under　the　green；　and　a　light　olive　under　the　blue。

〃The　above　paper　washed　with　a　solution　of　salt　of　iodine；　is　very　sensitive　to　light；　and　gives　a　beautiful　picture。　A　picture　thus　taken　was　placed　beneath　the　above　glasses；　and　another　beneath　four　flat　bottles　containing　colored　fluids。　In　a　few　days；　under　the　red　glass　and　fluid；　the　picture　became　a　dark　blue；　under　the　yellow　a　light　blue；　under　the　green　it　remained　unchanged；　whilst　under　the　blue　it　became　a　rose　red；　which　in　about　three　weeks　changed　into　green。　Many　other　experiments　of　a　similar　nature　have　been　tried　since　that　time　with　like　results。

〃In　the　summer　of　1843；　when　engaged　in　some　experiments　on　papers　prepared　according　to　the　principles　of　Mr。　Talbot's　calotype；　I　had　placed　in　a　camera　obscura　a　paper　prepared　with　the　bromide　of　silver　and　gallic　acid。　The　camera　embraced　a　picture　of　a　clear　blue　sky；　stucco…fronted　houses；　and　a　green　field。　　The　paper　was　unavoidably　exposed　for　a　longer　period　than　was　intendedabout　fifteen　minutes；a　very　beautiful　picture　was　impressed；　which；　when　held　between　the　eye　and　the　light；　exhibited　a　curious　order　of　colors。　　The　sky　was　of　a　crimson　hue；　the　houses　of　a　slaty　blue；　and　the　green　fields　of　a　brick　red　tint。　Surely　these　results　appear　to　encourage　the　hope；　that　we　may　eventually　arrive　at　a　process　by　which　external　nature　may　be　made　to　impress　its　images　on　prepared　surfaces；　in　all　the　beauty　of　their　native　coloration。〃

PHOTOGRAPHIC　DEVIATIONS。

Before　taking　leave　of　the　subject　of　photogenic　drawing；　I　must　mention　one　or　two　facts；　which　may　be　of　essential　service　to　operators。

It　has　been　observed　by　Daguerre；　and　others；　in　Europe；　and　probably　by　some　of　our　own　artists；　that　the　sun　two　hours　after　it　has　passed　the　meridian；　is　much　less　effective　in　the　photographic　process；　than　it　is　two　hours　previous　to　its　having　reached　that　point。　This　may　depend　upon　an　absorptive　power　of　the　air；　which　may　reasonably　be　supposed　to　be　more　charged　with　vapor　two　hours　before　noon。　The　fuse　of　the　hygrometer　may　possibly　establish　the　truth　or　falsity　of　this　supposition。　　The　fact；　however；　of　a　better　result　being　produced　before　noon　being　established；　persons　wishing　their　portraits　taken；　will　see　the　advantage　of　obtaining　an　early　sitting；　if　they　wish　good　pictures。　On　the　other　hand；　if　the　supposition　above　mentioned　prove　true；　a　too　early　sitting　must　be　avoided。

If　we　take　a　considerable　thickness　of　a　dense　purple　fluid；　as；　for　instance；　a　solution　of　the　ammonia…sulphate　of　copper；　we　shall　find　that　the　quantity　of　light　is　considerably　diminished；　at　least　four…fifths　of　the　luminous　rays　being　absorbed；　while　the　chemical　rays　permeate　it　with　the　greatest　facility；　and　sensitive　preparations　are　affected　by　its　influence；　notwithstanding　the　deficiency　of　light；　nearly　as　powerfully　as　if　exposed　to　the　undecomposed　sunbeams。

It　was　first　imagined　that　〃under　the　brilliant　sun　and　clear　skies　of　the　south；　photographic　pictures　would　be　produced　with　much　greater　quickness　than　they　could　be　in　the　atmosphere　of　Paris。　It　is　found；　however；　that　a　much　longer　time　is　required。　Even　in　the　clear　and　beautiful　light　of　the　higher　Alps；　it　has　been　proved　that　the　production　of　the　photographic　picture　requires　many　minutes　more；　even　with　the　most　sensitive　preparations；　than　it　does　in　London。　It　has　also　been　found　that　under　the　brilliant　light　of　Mexico；　twenty　minutes；　and　half　an　hour；　are　required　to　produce　effects　which　in　England　would　occupy　but　a　minute；　and　travellers　engaged　in　copying　the　antiquities　of　Yucatan　have　on　several　occasions　abandoned　the　use　of　the　photographic　camera；　and　taken　to　their　sketch　books。　Dr。　Draper*　has　observed　a　similar　difference　between　the　chemical　action　of　light　in　New　York　and　Virginia。　　This　can　be　only　explained　by　the　supposition　that　the　intensity　of　the　light　and　heat　of　these　climes　interferes　with　the　action　of　the　ENERGIC　rays　on　those　sensitive　preparations　which　are　employed。

*　I　would　here　take　occasion　to　remark　that　our　country　man；　Dr。　Draper；　is　very　frequently　quoted　by　Mr；　Huut　in　his　〃Researches。〃

LUNAR　PICTURESDRUMMOND　LIGHT。

The　Roman　Astronomers　state　that　they　have　procured　Daguerreotype　impressions　of　the　Nebula　of　the　sword　of　Orion。　Signor　Rondini　has　a　secret　method　of　receiving　photographic　images　on　lithographic　stone；　on　such　a　prepared　stone　they　have　succeeded　in　impressing　an　image　of　the　Nebula　and　its　stars；　〃and　from　that　stone　they　have　been　enabled　to　take　impressions　on　paper；　unlimited　in　number；　of　singular　beauty；　and　of　perfect　precision。〃　Experiments　have；　however；　proved　that　〃no　heating　power　exists　in　the　moon's　rays；　and　that　lunar　light　will　not　act　chemically　upon　the　iduret　of　silver。〃

It　was　at　one　time　supposed　that　terrestrial　or　artificial　light　possessed　no　chemical　rays；　but　this　is　incorrectMr。　Brande　discovered　that　although　the　concentrated　light　of　the　moon；　or　the　light　even　of　olefiant　gas；　however　intense；　had　no　effect　on　chloride　of　silver；　or　on　a　mixture　of　chloride　and　hydrogen；　yet　the　light　emitted　by　electerized　charcoal　blackens　the　salt。　At　the　Royal　Polytechnic　Institution　pictures　have　been　taken　by　means　of　sensitive　paper　acted　upon　by　the　Drummond　Light；　but　it　must　of　course　be　distinctly　understood；　that　they　are　inferior　to　those　taken　by　the　light　of　the　sun；　or　diffused　daylight。

If　our　operators　could　manage　to　produce　good　pictures　in　this　way　they　would　put　money　in　their　pockets；　as　many　who　cannot　find　time　during　the　day　would　resort　to　their　rooms　at　night。　I　throw　out　the　hint　in　hopes　some　one　will　make　the　experiment。

I　have　learned；　since　the　above　was　written；　that　an　operator　in　Boston　succeeded　a　short　time　since　in　procuring　very　good　pictures　by　the　aid　of　the　Drummond　Light；　but　that　the　intensity　of　the　light　falling　directly　upon　the　sitter's　face　caused　great　difficulty；　and　he　abandoned　it。　This　may；　probably；　be　remedied　by　interposing　a　screen　of　very　thin　tissue　paper　tinged　slightly　of　a　bluish　color。



CHAP。　XII。

ON　COLORING　DAGUERREOTYPES。


Nearly；　if　not　quite　all　the　various　colors　used　in　painting　may　be　made　from　the　five　primitive　colors；　black；　white；　blue；　red　and　yellow；　but　for　the　Daguerrean　artist　it　would　be　the　best　policy　to　obtain　such　as　are　required　by　their　art　already　prepared。　　In　a　majority　of　cases；　the　following　will　be　found　sufficient；　viz。

Carmine。

Prussian　Blue。

White。

Chrome　Yellow；　Gamboge；　Yellow　Ochre；　or　all　three。*

*Gamboge　is　best　for　drapery；　Ochre　for　the　face。

Light　Red。

Indigo。

Burnt　Sienna。

Bistre；　or　Burnt　Umber。

If；　in　coloring　any　part　of　a　lady's　or　gentleman's　apparel；　it　is　found　necessary　to　produce　other　tints　and　shades；　the　following　combinations　may　be　used：

OrangeMix　yellow　with　red；　making　it　darker　or　lighter　by　using　more　or　less　red。

PurpleThis　is　made　with　Prussian　blue；　or　indigo　and　red。　Carmine　and　Prussian　blue　producing　the　richest　color；　which　may　be　deepened　in　the　shadows　by　a　slight　addition　of　indigo　or　brown。

GreensPrussian　blue　and　gamboge　makes　a　very　fine　green；　which　may　be　varied　to　suit　the　taste　of　the　sitter　or　operator；　by　larger　portions　of　either；　or　by　adding　white；　burnt　sienna；　indigo；　and　red；　as　the　case　may　require。　These　combinations；　under　different　modifications；　give　almost　endless　varieties　of　green。

BrownMay　be　made　of　different　shades　of　umber；　carmine　and　lamp…black。

Neutral　tintIs　composed　of　indigo　and　lamp…black。

CrimsonMix　carmine　and　white；　deepening　the　shaded　parts　of　the　picture　with　additional　carmine。

Flesh　ColorThe　best　representative　of　flesh　color　is　light　red；　brightened　in　the　more　glowing　or　warmer　parts；　wit