74 TRANS. OP THE ACAD. OF SCIENCE. 



immediately on the banks of a large river, the fall of rain is 

 heavier than in the interior. Still farther oft* the river, and 

 especially in the great prairies east as well as west of us, the 

 fall of rain is stated to be still smaller. 



The following results of our comparative observations may 

 be considered as substantiated : 



1. The Temperature is lower in the country than in the 

 city. 



2. The Difference is greatest at night and least in the mid- 

 dle of the day. 



3. It is greater in summer and autumn, and less in winter 

 and spring. 



4. The daily as well as annual Ranges of the Thermometer 

 are therefore greater in the country, and greatest in summer 

 and autumn. 



5. The Evaporation is greater in the city than in the coun- 

 try, and the difference is greater in daytime than at night, 

 and greater in summer than in winter. 



6. The Relative Humidity is greater in the country than 

 in the city ; the difference is smaller in winter, and greater in 

 spring, summer, and autumn — during the months of active 

 vegetation. 



7. The annual Fall of Rain is greater in the city than in 

 the country, though in some months this rule may be re- 

 versed. 



These facts, especially 2, 4 and 6, explain to a great extent 

 the difference in the hygienic condition of city and country ; 

 but it would be foreign to the subject of this paper further to 

 enter into this interesting and eminently practical investi- 

 gation. 



