230 AGRICULTURAL REPORT. 



and fatal. So it is in the close, imveutilated, and undrained, or imder- 

 gronnd stables of cities, -with air loaded to suffocation with the pro- 

 ducts of respiration and putrefaction. In these the mortality i^roves 

 far in excess of that of the horses in the better-appointed stables, or in 

 the country-. A revicTv of the whole subject shows very conclusively 

 that an excess of ozone in the atmosphere cannot be accepted as the 

 One cause, or the main cause, of influenza. 



Again, it is diflQcult to estimate the amount of ozone in the air. Ni- 

 trous acid, which often exists in great amount near the surface of the 

 earth, which, like ozone, is produced in large quantities during thun- 

 der-storms, and like it decomposes organic matter in the air, has pre- 

 cisely the same reaction with ozone on iodized starch papers. Ozone, 

 moreover, is always present in larger amount at the higher altitudes, 

 but influenza shows no such predilection for the hills. It has, ou the 

 other hand, during the recent epizootic, shown a decided preference for 

 the valleys, along which run the great railroad-tracks, as evinced by its 

 earlier debut in such places. Agaia, the amount of ozone varies con- 

 stantly ou the sea-shore from the great evaporation and the ever-chang- 

 ing condition of the electricity, and a sea-side residence has been accord- 

 ingly advised as a safeguard against the evil effects of an excess of ozone. 



But the recent epizootic had its origin near the border of a large lake, 

 and has in the main prevailed earlier and more severely in the large 

 towns on the Atlantic sea-board than in inland districts. As examples, 

 may be mentioned IS'ew York, Brooklyn, Jersey City, and Boston, at- 

 tacked on or about October 22; Portland, Maine, Newport, Ehode Island, 

 and iSTew Haven, Connecticut, October 23 ; Portsmouth, Virginia, Novem- 

 ber 1 : and Charleston, South Carolina, November 2: whereas it only 

 appeared in Washington County, and Kingston, New York, on Novem- 

 ber 1 ; Cooperstown on November G, and in Scranton, Forest County, 

 Clearfield County, and elsewhere in Pennsylvania about November 14. 

 Dropsies and other dangerous complications were also very jirevalent 

 in these sea-board cities. 



Through the favor of Professor Kedzie, of the Michigan State Agri- 

 cultural College, I am enabled to present the following letter, embody- 

 ing his observations on the amount of atmospheric ozone before and 

 diiring the prevalence of the disease : 



MiCHiG.iN State Agricultural College, 



Chemical Department, Lansing, Deceviher 16, 1872. 



Dear Sir : Your favor of 11th instant, asking information in regard to tlie amount 

 of atmospheric ozone observed at th^is place in connection vrith the influenza in horses, 

 is received, and it gives me great pleasure to comply with your request. 



The observations on atmospheric ozone have been taken at this college only during 

 two years — a narrow ground for any broad generalizations. The observations are 

 taken twice a day, viz, from 7 a. m. to 2 p. m., the day observations ; and from 9 p. m. 

 to 7 a. m., night observations. They are taken by exposing a slip of Schonbein's test- 

 paper (moistened) to the air in a shady place, but freely exposed to the air. At the 

 close of the observation the paper is again moistened with distilled Avater and com- 

 pared with the scale. The scale has for its extremes the slightest perceptible shade 

 of purple, which is marked 1, and the deepest purple- blue characteristic of iodide of 

 starch; marked 10, the space between 1 and 10 being toned to give gradation of the 

 scale. The place of observation is such as gives pure country air. The night obscrva- 

 vations give a larger amount of ozone for two reasons : 1st, the greater length of time, 

 and 2d, the larger amount of atmospheric moisture. 



Immediately preceding the epizootic, a marked incre;;se of ozone was observed— so 

 marked as to call special attention to the fact. During September the average amount 

 of ozone by day was 1.40, and by night 1.8G; for October, 1.9.3 by day, and 3.18 by 

 night, with a rapid increase durinrj the last three daijs of the month. Early in November 

 the disease made its appearance, and during this mouth the averange of ozone by day 

 was 4.60, and by night 6.17. The average of December to this date is 5..% by day, C.tK5 

 by night. A comparison of the amount of ozone during corresponding periods of 1871 



