lOS UNITED STATES. ^ 



natural seasons. For he thinks the Springs are 

 much colder, and the Autumns more temperate, 

 than in earlier times, insomuch that cattle are not' 

 housed so soon, by one month, as they were in form- 

 er years : He refers the opinion of the amelioration 

 of our climate, to the difference of clothing and sen- 

 sation between youth and old age, in Winter and 

 Summer: He ad^.pts the opinion of Dr. Wiliiamsonf 

 respectii g the diminution of the cold in the southern, 

 being occasioned by the cultivation of the northern,, 

 parts of Europe ; but, he says, no such cultivation 

 has taken place in the countries which lie to the north- 

 west of Pennsylvania, nor, in his opinion, do the par- 

 tial and imperfect improvements in the north-west- 

 ern par ts of the state, appear to be sufficient to lessen 

 the cold, even in Philadelphia. He says, finally, that 

 he has been able to collect no facts which dispose him. 

 to believe, that the Winters were colder before the 

 year 1740, than they have been since. 



Besides that there is some other cause operating to 

 affect the climate, independently of the clearing of 

 the country, is evident, from the fact already men- 

 tioned from Mr. Dunbar, viz. the increasing cold- 

 ness of the Mississippi Territory in W^inter, and 

 greater heat in Summer. 



Dr. Mitchell objects to Mr. Volney*s theory of the 

 liorth-west wind o't Nordi America, and offers the 

 following to supply the defect : 



The great expanding power (he observes) acting ' 

 upon the atmosphere is caloric. This is more pow- 



* Rush's Works, vol. i. 

 t Amer. PhU. Trans, vol, i. 



