ThenatureofthechangewhichtheioduretofsilverundergoesonDaguerreotypeplates，throughtheactionoflight，Mr。Huntconsiderstobeadecidedcaseofdecomposition，andcitesseveralcircumstancesinproofofhisposition。
ThesewithotherfactsgivenbyMr。HuntinhisgreatworkonthePhotographicart，buttovolumnioustoincludeinavolumeofthesizetowhichIamobligedtocofinemyself，shouldbethoroughlystudiedbyallDaguerreotypists。
PRISMATICANALYSIS。——Themostrefrangibleportionofthespectrum，（onaDaguerreotypeplate）appears，aftertheplatehasbeenexposedtothevaporofmercury，tohaveimpresseditscolors;
thelightanddelicatefilmofmercury，whichcoversthatportion，assumingafinebluetintaboutthecentralparts，whicharegraduallyshadedoffintoapalegrey;andthisisagainsurroundedbyaverydelicaterosehue，whichislostinabandofpurewhite。
Beyondthisaprotectinginfluenceispowerfullyexerted;