THE CAMERA 



217 



HOW THE CAMERA SHOWS THAT RAILROAD DUST IS TINY CINDERS. 



cinders were microscopic. Tins accu- 

 mulation of dust came from the rail- 

 road about forty rods away and was 

 formed in the winter, when the win- 

 dows on that side of the laboratory are 

 closed. The dust was fine enough to 

 float in the air and to work itself into 

 the room with the currents of air that 

 were working- in through the spaces 

 around the windows. If the air forty 

 rods from the railroad is thus filled 

 with microscopic cinders, it makes one 

 wonder what must be the condition of 

 the air in the railroad station, and also 

 how far from the track the cinder dust 

 may be carried. This would be an 

 interesting" field for investigation by 

 one who has time to make a study of 

 such accumulated dust at various dis- 

 tances from a railroad. At any rate, 

 I found by careful examination under 

 the microscope that as is here shown 

 in the photomicrograph the structure 

 ot the microscopic cinders was prac- 

 tically the same as the structure of 

 such cinders as would be delivered by 

 the wag-on load for making walks or 

 for grading. 



These investigations suggested one 

 more trial. I went to the book shelves 

 in another room and there searched for 

 a volume that had been the longest un- 

 used. I coated a glass slip with a very thin 

 layer of mucilage and touched this 

 against the dusty edge of the book. 

 Placing it under the microscope I 

 found that the deposit was composed 

 of characteristic white fibers similar 

 to those from the bedroom, but not 



so long and evidently to a large extent 

 of the fibers of wood. It seems that 

 the floor must wear away under con- 

 stant use and the tramping of many 

 feet, and that the tiny particles of wood 

 thus rasped oft* are much the same as 

 those pulled from old fence rails by 

 hornets for paper making. These short 

 fibers of wood from the floor float in 

 the air and settle wherever they find a 

 lodging place. Mingled with these, are 

 occasionally the fibers of cloth, but 

 basis is made up mostly of very fine 

 soil. This seems to be ordinary soil 

 that has been brought in on the shoes, 

 and pulverized so fine on the floor that 

 the unseen and unnoticed currents of 

 air carry it in all directions. 



When one sees a ray of light in a 

 darkened room, he is astonished be- 

 cause the air contains such myriads of 

 floating particles, but the light that 

 they reflect shows them plainly and 

 the microscope applied to the accu- 

 mulated dust in that room will reveal 

 the character of the material there 

 floating and deposited. Nature has 

 evidently realized this condition of 

 things, and in the structure of our nos- 

 trils by the mucous coating and by the 

 sieve of hairs at the entrance, has made 

 an effort to prevent at least a portion 

 of these irritating- and possibly patho- 

 genic particles from getting into our 

 lungs. Here certainly is a valid argu- 

 ment for the perfect cleanliness of a 

 room, and for wiping the floor with a 

 wet cloth or with some of the commer- 



