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



single definite impressions. However great Moser's assump- 

 tion may be, there are many achievements of modern photo- 

 graphy that would be as surprising if they were not so 

 familiar. I have not the means of knowing the precise form 

 of Moser's methods : in the experiments which follow there 

 is usually contact and light pressure, and if they are not 

 wholly analogous, they may for that cause help to generalize 

 the idea : in none of these is electricity applied. 



A piece of mica is freshly split, and a coin lightly pressed 

 for 30 seconds on the new surface : a breath-image of the 

 coin is left behind. At the same time it may be noticed that, 

 the breath causes abundant iridescence over the surface, whilst 

 it is in a fresh state. It is not clear how the electricity of 

 cleavage can have an active agency in the result. 



It is familiar to most people that a coin resting for a while 

 on glass will give an outline of the disk, and sometimes faint 

 traces of the inner detail when breathed upon. 



An examination-paper, printed on one side, is put between 

 two plates of glass and left for ten hours, either in the dark 

 or the daylight: a small weight will keep the paper in continu- 

 ous contact, but this is not necessary if thick glass is used. A 

 perfect breath-impression of the print is made, not only on 

 the glass which lay against the print but also on that which 

 faced the blank side of the paper. Of course the latter reads 

 directly, and the former inversely ; the print was about one 

 year old, and presumably dry. 



More often both impressions are white, sometimes one or 

 other or both are black. At other times the same one may be 

 part white and part black, and they even change while being 

 examined. 



During a sharp frost with east winds early in March, 1890, 

 these impressions of all kinds were easy to produce, so as to 

 be quite perfect to the last comma ; but in general they are 

 difficult, more especially those from the blank side. 



At the best period those from the blank side of the paper 

 were white and very strong ; also there were white spots and 

 blotches revealed by the breath. They seemed to correspond 

 with slight variations in the structure of the paper, and suggest 

 an idea that the thickness of the ink or paper makes a minute 

 mechanical indentation on the molecules : the state of these 

 is probably tender and sensitive under certain atmospheric con- 

 ditions, as happens with steel in times of frost. 



The following experiments easily succeed at any time : — 

 Stars and crosses of paper are placed for a few hours beneath 

 a plate of glass : clear white breath-figures of the device will 

 appear. A piece of paper is folded several times each way 



