( ^ ) 



atov whose works so loudly proclaim his wisdom, aud the extent of his benevolence and attention to the 

 rable living objects which he has formed. 



§. XVIII. 



It is highly probable, that the periods of the migrations of birds will be found to be more or less uniform in pro- 

 portion as the climates of the countries to which they migrate are more or less variable in their temperature. It is, 

 perhaps, upon this principle, that we are to e.xplain the difference of the times of the arrival and departure of the 

 birds of Pennsylvania, and other parts of North-America. The climates of these countries are extremely variable ; 

 I suppose more so than most other countries that are known to us. If, as has been supposed by many writers, the 

 hand of man, by clearing and by cultivating the sm'face of the earth, contributes essentially to the greater uniformity 

 in the temperature of climates, it is reasonable to conjecture, that the time will come, when the periods of the 

 migrations of our birds will be more constant and fixed. For in North-America, especially the United-States, the 

 progress of popidation, and of clearing and cultivating the earth, is more rapid and immense than in any other 

 portion of the world. 



§. XIX. 



It would be a very curious subject of inqiuiy, — What changes have taken place in the periods of the arrival and 

 disappearance of the passenger-birds, in those countries in which observations have long been made by the ancient 

 poets, and by natm-ahsts ? Perhaps, an investigation of this question would, in some degree, iUastrate the changes 

 which climates are said to have undergone. Thus, the time of the Swallow's coming into Italy, is particularly 

 mentioned both by Columella and by Pliny,* and it may be gathered also from a beautiful passage in the Georgics 

 of Virgil.t I)o the periods mentioned by these writers correspond with the periods of the arrival of this bird, in 

 the same comitry, at present ? If the climate of Italy, within the last seventeen or eighteen himdred yeai-s, has 

 altered as much as it is, by many ingenious men, thought to have done, it is not likely that the Swallow now visits 

 that country at the same time it did formerly, in the days of Virgil, and the naturalists whom I have mentioned. I 

 am sorry that I cannot, without some trouble, ascertain the question. 



§. XX. 



The fourth column of the tables will enable the curious naturalist to form some idea of the temperature of our 

 climate (by showing the time of leafing, flowering, planting, &c. of a considerable number of vegetables, both 

 native and foreign) ; at the same time, that it will point out, in a number of instances, the coincidence between 

 this progress in vegetation and the arrival and disappearance of the migratory birds. This last has long been deemed 

 an interesting subject by naturalists, though I am inclined to think, that they have often imagined, that this coinci- 

 dence is greater than it really is. 



§. XXI. 



I will not deny, that there is a very remarkable conformity between the vegetation of some plants and the arrival 

 of certain birds of passage. This, perhaps, is especially the case in those countries the climates of which are the 

 most regidar in their seasons. Linnmus has observed, that the Wood-Anemone (Anemone nemorosa) blows in 

 Sweden on the arrival of the Common Swallow, | and that the Marsh-Marygold (Caltlia palustris) blows when the 



' Columella says, tlio Swallow visits Italy about the twentieth or tweiity-lhird of February. The following are his own words: " Decimo Calendas 

 >rartii leo deflixit occiderc, veuti scptentrionalea, qui vocantur ornithiec, per dies triginta esse solent, turn et hirundo advenit." In another place, he says, 

 ■• Septiino Calendas Martii ventosa tempestas, hirundo conspicitur." De Ee Euslica. Pliny says, this bird appeared on the twenty-second of February : 

 " Octavo calendas Martii 



Georgic. IV. $05—307. I Hirundo urbica. 



