268 MR. R. A. SMITH ON A SEARCH FOR 



Dancer's the air at that place may have communicated 

 them. I answer that, before it was opened, a good glass 

 could detect floating matter ; some of it, however, as in the 

 microscope, proved indefinite enough. 



^^ Finding this, and fearing that the long time needful 

 to collect liquid from the atmosphere might expose it also 

 to much dust, I used a bottle of about lOO cubic inches 

 dimensions, and putting into it a very little water, not 

 above five cubic centimetres, I pumped out the air of the 

 bottle, allowing the air of the place to enter. This was 

 done six times for each sample, the water shaken each 

 time, and the result examined. This was done with the 

 same bottle that was used in my early experiments with 

 permanganate, and by the same method, except that water 

 instead of that salt was used. At first considerable num- 

 bers of moving particles were found ; but it was needful 

 to examine the water used, and here occurred a difficulty. 

 It was not until we had carefully treated with chemicals 

 and then distilled the water again and again that we could 

 trust it. Particles seemed to rise with the vapour ; and if 

 so, why not with the evaporating water of impure places. 



" Having kept an assistant at the work for a week, and 

 having myself examined the air of three cow-houses, I 

 came to the conclusion that the air of cow-houses and 

 stables is to be recognized as containing more particles 

 than the air of the street in which my laboratory is, and 

 of the room in which I sit, and that it contains minute 

 bodies, which sometimes move, if not at first, yet after a 

 time, even if the bottle has not been opened in the in- 

 terval. There is found in reality a considerable mass of 

 debris, with hairs or fine fibres, which even the eye, or at 

 least a good pocket-lens, can detect. After making about 

 two dozen trials, we have not been able to obtain it other- 

 wise. Even in the quiet office at the laboratory there 

 seemed some indications. 



