HAS OUR CLIMATE CHANGED? 669 



This popular opinion of change of climate through agricultural 

 operations is far from being restricted to America. In Western Eu- 

 rope there is a belief that a great amelioration has taken place in all 

 the Baltic countries since the time of the Roman domination. 



In many instances these popular impressions are contradicted by 

 well-ascertained facts. Thus, as respects the Baltic, there are records 

 of the time of the breaking of the ice in some of the great rivers, such 

 as the Dwina and Neva, for several centuries. These show that, dur- 

 ing the last 300 years, the variation amounts but to a fraction of a 

 single day. 



Such fragments as have been preserved of the observations of the 

 first discoverers of North America the Icelandic voyagers have 

 been supposed to prove a change in the climate of New England dur- 

 ing the last 800 years, it being affirmed that the vine formerly flourished 

 in regions where it cannot now exist. One of the first papers commu- 

 nicated to the American Philosophical Society, in Philadelphia, was by 

 Dr. Williamson, offering proof that, during the previous 40 or 50 years, 

 a very great climate change had taken place ; he attributed it to culti- 

 vation. Soon afterward, Dr. Williams, of Harvard University, offered 

 evidence that the climate of Boston had changed 10 or 12 in about 

 160 years. A close examination of the evidence by more recent au- 

 thorities has, however, shaken these conclusions. Thus, as regards 

 the Icelandic voyages, it is shown that the description they give of 

 the forest-growth of New England is the same that might be given 

 now. Humboldt, in his " Views of Nature," comes to the conclusion 

 that there has not been any change in the climate of the United States 

 since its first colonial settlement, and in this, Noah Webster, Forry, 

 and other American writers agree. 



It is evident, however, that in a rapidly-growing city there are 

 several local causes which may be assigned as giving origin to an 

 increase of temperature. The quantity of fuel burnt increases with 

 increased population and with the number of houses, and this must 

 exert a perceptible effect in ameliorating the rigor of winter. More- 

 over, on sunshiny days, the reflection and radiation of the sun's 

 warmth from the vertical sides of the houses must tend in no incon- 

 siderable degree to raise the temperature locally, and aid in producing 

 a thaw. The facts observed in a city are hence not a complete guide 

 in the discussion of general climate changes. 



If our climate be gradually changing, if the heat of summer is be- 

 coming less excessive, and the cold of winter more moderate, there are 

 impending over us modifications in our social habits, and in many of 

 our business occupations. Not only is the settlement of this question 

 interesting in a meteorological or scientific point of view the sani- 

 tary, engineering, manufacturing, mercantile, and agricultural conse- 

 quences are also of the utmost importance. 



Impressed with these considerations, I was therefore led to extend 



