Dr. Forry on the Climate of the United States, 6)'c. 229 



and Danube, that " modem ages have not presented an instance 

 of a like phenomenon,''^ he says, "is contrary to all historical evi- 

 dence, and even to facts which took place during that author's life." 



Dr. W. dwells particularly upon the vegetables which flourish- 

 ed in the Augustan age in Gaul ; and these evidences, he regards 

 as our safest guides. He concludes with the following striking 

 remark : " Olives grow and mature there [the south of France] 

 precisely within the limits marked by Strabo and Pliny, and as 

 far as we can judge, not a league further north than they did 

 1800 years ago." But as respects the influence of temperature 

 on the geography of plants, Dr. W.'s remarks are defective, in 

 consequence of his limiting his comparisons to the mean annual 

 temperature of a locality, which is entirely subordinate to the 

 distribution of the temperature among the different months of the 

 year. It is true, De Candolle had not written in 1799, but in 

 publishing in 1843, it should not have been forgotten that a new- 

 era had arisen in meteorology. 



Dr. Webster's final conclusion from this extensive and most 

 learned array of historica,l facts, is, for the first essay, that, as re- 

 spects both the old and new world, " the hypothesis of a modera- 

 tion of climate appears to be unsupported." And, for the second — 

 " But we can hardly infer, from the facts that have been yet col- 

 lected, that there is, in modern times, an actual diminution of the 

 aggregate amount of cold in winter, on either continent." 



Now, as Dr. W.'s views relative to the influence that clearing 

 the country of its forests exercises upon the seasons of the year, 

 also correspond remarkably with our own deductions, we cannot 

 fail to discover a marked coincidence in the similarity of his con- 

 clusions and that previously expressed by ourselves : " All obser- 

 vations then, thus far, confirm the belief in the general stability 

 of climates. As regards the seasons, it will be shown, however, 

 that in countries covered with dense forests, the winters are lon- 

 ger and more uniform than in dry, cultivated regions, and that in 

 summer, the mean temperature of the latter is higher. Hence, 

 in regard to the opinion generally entertained, that the climate of 

 Europe has been very much meliorated since the days of Julius 

 Cassar, it is clearly apparent, from the foregoing facts, that it is 

 far from being sustained by evidence sufficient to enforce convic- 

 tion. But, at the same time, while it is obvious that no material 

 change has taken place, for the last two thousand years, in the 



Vol. xLvii, No. 2.— July-Sept. 1844. 30 



