I have long been a reader of your valuable e long been e de of yo 1 ble ma and have been much interested nma ny of tl e omm a on o Elec ty a d Chemical Science, -which have appeared fron time to t me ol mn II e bee e pe mentingon Heliochromy during my lei s e 1 o o a fe weeks pa t and am nd [cedtog eyo tie e t ofn e penment 1 n tl e 1 ope tl t otl e n be led o p o en e 1 em mo e easl Tl e d o e e of M Np e \ o He liochromy have been announced to the publ for some time ; I first saw them on page 3, To 7 ert fi Ame can b 111 a e 1 e d of o 0 e epeating them. An outline ol M. Niepce1, pop n be fo nd n 1 e Ann 1 of * en he D co e tl e ye 1 t ubstantiallythefollowlng:—Make a solution of tl e 1 londe of oppe and on bo t one part of the mixed chloride with three or fo of water. The plate to be prepared is to be attached to the positive pole of a galvanic bat-tery tl e negati e po e o 1 1 (a p atinum pi e) imn e sed n 1 e lu on nd tl en tself mme edf I art time depending on the strength of the battery. The color of the plate rapidly changes from the chlorine of the mixed 1 ide alt ki g t s a e to a ed ilac brown, tnd even nearly black. It 1 oild be taken out when the plate ha ac q red a lilac or brownish tint if sufficiently f not let t en n lit e longe V, tl h nged o nee1 to) en o g tl e po o c p nd 1 ging t vitl dil te lpl c d tl 11 yd ogen not e ol ed too pidly from the platinum plates, it will take hed in rain or distilled water and dried c refully over a spirit lamp. The color cl n ge tl e pi te 1 e ted tl o gl o 1 d of brown and ted, and is at its most ens t e t e wl en t akes a cherry red. It ihould not. however, be heated n o e 1 Fahr.. or the surface will scale off. All 1 e ope tions n be pe o n ed n open d yl gl t ( o d g of co e 1 e d ect y of tie n) deed e n mount of 1 ght en to be e e j n tl e j. ep tion of tl e pi te Tl e pi e f ell p ep ed wll no p esent a beautiful red enamelled-like uf ce p tl t n 1 ent b t 111 1 owing noprtoite leed irfce beneatl nd Tleob e t to be cop ed olo edli hog pi vill ns e plced ntlecle 1 git of tie n ind the prepared plate e posed o ! lo time ry ng 1 tl e b g tne of tl e liglt ndtlepe lenceoftle t e y n, tie tmoplee Itt k f on t o to tl ee nd on five to six to obtain a good p e If the process be successful, a perfect copn of pesenedontlepl te ( nd t vil e en ble mn ep ting) b tbe n 1 fine n de I tl e pi e be dipped befo e pi c ng t n I e me n e k 1 tion of tl e 11 o de of di m tl e p o e 11 be m 1 cele ted nd tl e colo pe ed II eteda 0 otl e ccele o —tl e cl o de of o diumand bromine, the compound b o 1 drof onne c d I lo o 1 om c c JSi pe fi o de of cl ome Tl e 11 ac mmi tlepoce eyn I b td m n 1 tie**? L ncy of tie colo tie lldrofl o c MM 1 oo 1 omi aedsae lebet Tl e?$ fluoric acid acts very well with red and bi bla k lin o a da k ed Tl e otl er beti te b t tl e pi te 1 o d be e po d o t lily Ila etaken e good i ti e n an o andalalf b t t gene all ke tl eeoifo ' Tl e most annoy ng fail e nJH from m cal lating I e t me tugplak rg otl la afin * c fornaBd olo found, but not sufficiently developed. In ed b a Ikaline 1 a d I i c developed. A caraera witli an aperture n fo w g h p t ould bcag od ngement mical agents and heat very well, but are rapidly dissolved by the hyposulphite of soda. wa n "leible when the plate was taken from the ame a b ngtleeulpla of on a d b om .tft of potash, but tie o o e e lane 1 n leo gin 1 In 1 e cl lo o Ihavenotbeen ableto produce color on the mercurialized plate, tho gl 11 e not e pe mented m cl on t Tl p e en d f lie t but perhaps not impossible problem. It one o n o e colors might be produced in the o din p eti e b e po ng I e me c all zed m ge to I em c 1 ent be o e g ding Tl e colo n tl o be g 1 e to 1 em stry than to Hilloctirom M N ep e tl t no bodie b t 1 onne o chlorides are capable of producing co o ed m ge In nc ned 1 o e e to pect at when the problem of instantsneo pi tog pi m g 1 ed tl t fl o ne nil be lo nd as one of the principal, if not the pnnc p gent n tl e p od tion I shall be happy to hear from other expe- mente nd 1 11 be n cl pie ed f oftlen lo dm ketledi o e of at n taneo colo ednge tcedt de to MM Becq e el nd N ep e fo 1 e d o ee adlsofotlee dine vitl 1 I tl e I e m de tl em p blic I end o de ote p rt of the little leisure time I h e to A CAJI PEELL Dayton, Oh o P. S.—I omitted to mention that the pis e imetimes become solarized by long expo e Wlfn fl on prhaltleptieny omet me be ored by alkaline solutions A thin coating of some colorle n lso ery ad n geo to tl e p t e Tl p t ire ccele ed tl tl e fl o de of o dium or the chlorochromic acid seem to be dium or the chlorochromic acid seem to be quite .permanent in ordinary diffused light.