108 THE AMERICAN MONTHLY [June 



1,200 went out on the "Washing-ton." . While letters 

 could be carried out they could not be broug-ht in by 

 balloon. Carrier pig-eons were therefore sent out with the 

 balloons and permitted to bring- back dispatches. These 

 had to be lig-ht enoug-h in weig-ht for the pig-eons to carr3\ 

 Photo-microg^raphy was therefore resorted to. Messag-es 

 were copied on a sing-le sheet of paper and then reduced 

 to the most minute proportions. On their arrival in Paris 

 the characters were enlarged by the microscope. Each 

 message was then copied on a card and forwarded to the 

 person addressed. Each word cost ten cents and each 

 messag-e was limited to twenty words. Later the mes- 

 sag-es were printed from type and reduced still farther. 

 They were put on pieces of paper 1}{ by 1}4 inches. The 

 collodion films were rolled and enclosed in small quills 

 which were sewed to the tail feathers of the pig-eons. 

 The collodion films were ten times thinner and lig-hter than 

 paper. On arrival, in l*aris, the quills were split open and 

 the films rapidl}' unrolled in water containing- a few drops 

 of ammonia. The films were then dried and enclosed 

 within two plates of g-lass. They were then ready to be 

 deciphered by the microscope. This mode of reading- 

 was later supplanted by a projecting- lantern and electric 

 lig-ht. When thrown upon a larg-e screen four trans 

 scribers could work at once on each sheet contained 1,600 

 messag-es. At a later time, the films were photograg-hed 

 back to the scale of the orig-inal printed matter so that 

 each section was enlarg-ed from the most minute dimen- 

 tions to a form that could be read with perfect ease. 

 Then the teleg-rams were separated by scissors and each 

 person received a dispatch in fac-simile to the original 

 printed matter. Many of these dispatches are today 

 exhibited as specimens of photomicrog-raphy. 



Milk. — In Dr. Julius Nelson's investig-ation it was found 

 that milk in a cow's udder may have as hig^h as 10,000 

 bacteria per drop, that first drawn being most infected. 



Wanted :^ — Petrolog-ical microscope with accessories for 

 petrological work, instrument to be of superior g-rade and 

 in g-ood condition. Send description and price. 



