The method emplojed by A. Martin is the same as that which he described for taking positive pictures on glass. The metallic plate, covered in the usual manner (but upon both sides) with etching ground, is first coated with iodized collodion, then dipped in the solution of nitrate of silver, &c. The picture, when taken, is lreed from the unmodified iodide of silver by the bath or cyanide of silver washed with water, immersed in a solution of dextrine, and dried. The pns;idVPi may then make the sitre use of hie (IPMI1 Ihdt he does of the outline, which is usual]j, tidiiflcrred to the etching gi'iiuid hecomt impression on glass wiH pjeseive t*1'1*' dMv1. vsh*cli the op -lation OS pp"i,ivji ; i)l ,i("*lr'V imon tl-plate. Impie'-sioii'- taken in tb/ * upon vai-nished inetdliic plates of tn ' uirf o) even upon a cardboard, unite vwUi t',e iiipli'irs of pusitu" impressions upon f;1---, A ''lenrth dtid ticility o! transmit ( which t'a latter are deficient Tae method is nlo appln'pMe i oi)ii blorks — [Comply UP m