the history and practice of the art of photography-第21节

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n　opportunity　of　witnessing　its　effect。　We　are　especially　gratified　with　this　striking　improvement；　from　the　advantages　which　it　promises　to　the　Daguerrean　art。〃

〃It　is　admirably　designed　to　excite　a　new　interest　on　the　subject　through　the　community；　and　in　this　wayand　from　its　tendency　to　render　the　art　more　generally　useful；　and　to　elevate　and　distinguish　it　to　make　it　to　all　a　matter　of　more　general　importance。〃　　〃Yours　respectfully；　　〃M。　A。　ROOT。〃

In　our　second　edition；　we　hopewith　Mr。　Root's　permission　to　lay　the　whole　process　before　the　public；　although　our　artists　must　bear　in　mind　that　Mr。　Root's　patent　secures　to　him　the　exclusive　right　of　its　application。



CHAP。　XI。

ON　THE　PROBABILITY　OF　PRODUCING　COLORED　PICTURES　BY　THE　SOLAR　RADIATIONS　PHOTOGRAPHIC　DEVIATIONSLUNAR　PICTURESDRUMMOND　LIGHT。


Having　before　noticed　the　fact　that　some　advances　had　been　made　towards　taking　Daguerreotypes　in　color；　by　means　of　solar　rays；　and　expressed　the　hope　that　the　day　was　not　far　distant　when　this　might　be　accomplished；　I　here　subjoin　Mr。　Hunt's　remarks　on　this　subject。

Mr。　Biot；　in　1840；　speaking　of　Mr。　Fox　Talbot's　beautiful　calotype　pictures；　considers　as　an　illusion　〃the　hope　to　reconcile；　not　only　the　intensity　but　the　tints　of　the　chemical　impressions　produced　by　radiations；　with　the　colors　of　the　object　from　which　these　radiations　emanated。〃　It　is　true　that　three　years　have　passed　away；　and　we　have　not　yet　produced　colored　images；　yet　I　am　not　inclined　to　consider　the　hope　as　entirely　illusive。

It　must　be　remembered　that　the　color　of　bodies　depends　entirely　upon　the　arrangement　of　their　molecules。　We　have　numerous　very　beautiful　experiments　in　proof　of　this。　The　bi…niodide　of　mercury　is　a　fine　scarlet　when　precipitated。　If　this　precipitate　is　heated　between　plates　of　glass；　it　is　converted　into　crystals　of　a　fine　sulphur　yellow；　which　remain　of　that　color　if　undisturbed；　but　which　becomes　very　speedily　scarlet　if　touched　with　any　pointed　instrument。　This　very　curious　optical　phenomena　has　been　investigated　by　Mr。　Talbot　and　by　Mr。　Warrington。　　Perfectly　dry　sulphate　of　copper　is　white；　the　slightest　moisture　turns　it　blue。　Muriate　of　cobalt　is　of　a　pale　pink　color；　a　very　slight　heat；　by　removing　a　little　moisture；　changes　it　to　a　green。　These　are　a　few　instances　selected　from　many　which　might　be　given。

If　we　receive　a　prismatic　spectrum　on　some　papers；　we　have　evidence　that　the　molecular　or　chemical　disturbance　bears　some　relation　to　the　color　of　each　ray；　or；　in　other　words；　that　colored　light　so　modifies　the　action　of　ENERGIA　that　the　impression　it　makes　is　in　proportion　to　the　color　of　the　light　it　accompanies；　and　hence　there　results　a　molecular　arrangement　capable　of　reflecting　colors　differently。　Some　instances　have　been　given　in　which　the　rays　impressed　correspond　with　the　colors　of　the　luminous　rays　in　a　very　remarkable　manner。*　One　of　the　most　decided　cases　is　that　of　the　paper　prepared　with　the　fluoride　of　soda　and　nitrate　of　silver。　Sir　John　Herschel　was；　however；　the　first　to　obtain　any　good　specimens　of　photographically　impressed　prismatic　colorations。

*　See　Mr。　Hunt's　〃Researches　on　Light。〃

It　was　noticed　by　Daguerre　that　a　red　house　gave　a　reddish　image　on　his　iodized　silver　plate　in　the　camera　obscura；　and　Mr。　Talbot　observed；　very　early　in　his　researches；　that　the　red　of　a　colored　print　was　copied　of　a　red　color；　on　paper　spread　with　the　chloride　of　silver。**

**　In　1842；　I　had　shown　me　a　picture　of　a　house　in　the　Bowery；　which　had　been　repaired　a　few　days　previous；　and　in　the　wall　a　red　brick　left。　　This　brick　was　brought　out　on　the　Daguerreotype　plate　of　precisely　the　same　color　as　the　brick　itself。　The　same　artist　also　exhibited　to　me；　the　full　length　portrait　of　a　gentleman　who　were　a　pair　of　pantaloons　having　a　blue　striped　figure。　This　blue　stripe　was　fully　brought　out；　of　the　same　color；　in　the　picture。AMER。　ED。

〃In　1840　I　communicated　to　Sir　John　Herschel　some　very　curious　results　obtained　by　the　use　of　colored　media；　which　he　did　me　the　honor　of　publishing　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　lig