26 The Irish Nahiralist. 



duration of which must be learnt by a few trials, the exposed 

 portion of the paper becomes a deep blue, while that protected 

 remains white. The light, passing more or less through the 

 plant according as the different parts are more or less trans- 

 lucent;, of. course effects the .sensitive surface in proportion ; 

 awash "in clear water "fixes" the print by refnoving 'the 

 material sensitive to light. We now have a representation of 

 our plant in vdiite shaded with blue, on a blue ground. The 

 main objection to such prints is the colour, but this can, if de- 

 sired, be altered afterwards by suitable treatment. The advan- 

 tages of the blue paper are its cheapness, that no chemicals 

 are required, and that it does not readih' stick to the plants. 

 The next simplest paper to deal with is the printing-out platino- 

 type paper, often called "Pizzighelli paper," from its inventor. 

 It onl}^ requires fixing in dilute acid, and gives a pleasing 

 brownish-black colour, but the paper is costly. Both these 

 methods were practised by Mr. Joly most successfully last 

 summer, among the Swiss mountains, and with freshly gathered 

 flowers ; the printing frame and paper being readil}^ carried 

 in a satchel, and water being ever^'where abundant. To fix 

 the platinot3'pes probabh' the vinegar cruet would .suffice at a 

 pinch, if no more suitable acid were forthcoming. In this way 

 a charming collection ma^^ be formed, in many respects more 

 satisfactor}', and with less trouble than the collections of dried 

 specimens one often sees, though perhaps not scientifically so 

 valuable. 



But w^e are not confined to paper photographs. By acquir- 

 ing a little more skill in photographic manipulation, we 

 can make most effective lantern slides from the small flowers, 

 and also, as will be alluded to later, from many other natural 

 objects. Such are best made at night b}^ artificial light, as the 

 exposure is more easily regulated than b}^ daylight. I must 

 here assume that the ordinary- mode of making lantern slides 

 by contact from photographic negatives is understood, and for 

 details refer to the man}' treatises thereon obtainable from_ 

 photo-material dealers. The standard size for lantern slides 

 in this country being 3J inches square, we are practically 

 confined' to subjects coming within this area, and the method 

 of procedure is as follows : — A piece of clear glass is placed in 

 a suitable printing frame in the dark room, and the spray of 

 flowers, say of the bog pimpernel, Anagallis f aid la, is placed 

 thereon, a sheet of white paper beneath the frame facilitating 

 the arrangement ; over this is placed a sensitive plate, preferabl}' 

 one specially made for lantern work ; this must be done by 

 non-active light. The back of the frame being put in, the 

 whole is exposed to light, either gas, or an inch or two of 

 magnesium rjbbon. The plate is then developed and fixed, 

 and we have a negative of the flower, i.e. light or dark ground, 

 and with the lights and shades reversed. This may itself be 

 used as a lantern slide, or a print on to a second plate may be 



