Mr. W. B. Croft on Breath Figures. 185 



into small squares, then spread out and placed under glass : 

 the raised lines of the folds produce white breath-traces, and 

 a letter weight that was above leaves a latent mark of its 

 circular rim. 



Some writing is made on paper with ordinary ink and well 

 dried : it will leave a very lasting white breath-image after a 

 few hours' contact. If, with an ivory point, the writing is 

 traced with slight pressure on glass, a black breath-image is 

 made at once. Of course this reads directly, and the white 

 one inversely. It is convenient to look through the glass 

 from the other side for inverse impressions, so as to make them 

 read direct. 



Plates of glass lie for a few hours on a table-cover worked 

 with sunflowers in silk: they acquire strong white figures from 

 the silk. 



In most cases I have warmed the glass, primarily for the 

 sake of cleansing it from moisture ; but I have often gone to 

 a heat beyond what this needs, and think that the sensitive- 

 ness has been increased thereby. 



It is not not easy to imagine what leads to the distinction 

 between black and white, different substances act variously 

 in this respect. I have placed various threads for a few hours 

 under a piece of glass, which lay on them with light pressure: 

 wool gives black, silk white, cotton black, copper white. A 

 twist of tinsel and wool gives a line dotted white and black ; 

 after a time these traces show signs of developing into mul- 

 tiple lines as in the spark figures. 



Two cases have been reported to me where blinds with 

 embossed letters have left a latent image on the window near 

 which they lay ; it was revealed in misty weather, and had 

 not been removed by washing. I have not had a chance to 

 see these for myself, but both my informants were accustomed 

 to scientific observation. 



A glass which has lain above a picture for some years, but 

 is kept from contact by the mount, will often show on its 

 inner side an outline of the picture, always visible without 

 breath. It seems to be a dust figure easily removed : possibly, 

 heat and light have loosened fine paint particles, and these 

 have been drawn up to the glass by the electricity made in 

 rubbing the outer side to clean it. The picture must have 

 been well framed and sealed up ; most commonly dust and 

 damp get in and obscure such a delicate effect. 



I am at a loss to imagine simple causes for these varied 

 effects. I am not inclined to think, except in the case of 

 water-colours, which is hardly part of the inquiry, that there 

 is a definite material deposit or chemical change ; one 



