On rendering Writing indeJlruBible by Fire. 1 79 



with both thefe folutions were totally illegible. I then 

 threw the prepared paper thus written upon into the fire ; 

 and when it was wholly reduced to a coal, all the lines could 

 be read of a black colour on a white ground, fo that the cha- 

 Hfoers were almoft like thofe written with common ink on 

 white paper. If it be required to make the folutions of 

 <rold and antimony black, that the words written with them 

 may be more dininguifhable before the paper is burnt, it 

 will only be neceffary to add a little common ink to them, 

 but fuch as contains as fmall a quantity as poflible of the 



fulphite of iron*. 



I dipped paper which had been prepared with liquor of 

 flint in a faturated folution of nitrite of zinc, and fuffered 

 it to become exceedingly dry in the fun. I then wrote on 

 feveral bits of this paper with the folutions of different me- 

 tals, and a few hours after reduced them all to coal, by 

 holding them one after the other in the fire. Charafters 

 written with diffolved nitrite of copper appeared of the co- 

 lour of metallifed copper; thofe written with diffolved ni- 

 trite of iron, or bifmuth, of a yellow colour; thofe with 



« In the fame manner as charred paper is made to aflame a white co- 

 Jour when it has been before warned over with a mixture of gum arable 

 and magnena, it may be made to affume any other colour if the paper be 

 dipped fometimes in one and fometimes in another of the above-ment.oned 

 folutions as the chancers on the charred paper will then affume fome- 

 times one colour and fometimes another. If paper, for example, which 

 has been (baked Id liquor of flint, be held a-httle in a lolunon of fulphite 

 of copper, and then dried, the paper will affume a beautiful green colour. 

 If the paper be burnt, it affumes a copper colour. If you wnte on paper, 

 already tinged green, with any metallic folutions of metals which are not fo 

 eaf.ly decompofed by the adion of the fire, Angular phenomena will be 

 dbferved If you write on it with fulphite of iron, the chafers will be 

 read of a yellowiih colour. When the paper is reduced to coal, the cha- 

 rters are ftill feen yellow. If you write with diffolved nitrite of anti- 

 monv, the characters appear whitifh. If the chamfer, are 

 fuch paper with nitrite of zinc, they arc nmf.ble , but when the paper » 

 reduced to coal, they appear of a film colour, &c 



jsj a diffolved 



