268 tempeeatuee: changes upon cleaeing of foeests. 



most liable to damage by late spring-frosts, that happen after vegeta- 

 tion has started, or in autumn, before the growth of the young wood 

 has hardened.^ 



Among the questions of greatest practical interest in this inquiry, 

 affecting not only the affairs of sylviculture, but also of agriculture and 

 horticulture in every department, is " To what extent is the temperature 

 of a country affected by the presence of forests, and how is it modified 

 by their removal f We have already in this report given the results of 

 instrumental observations made at several stations in Euroi)e upon this 

 particular subject. As yet, "wo have nothing of this kind upon which 

 to base conclusions, and must depend upon opinions and observations 

 of less reliable kind ; but still, as coming from men accustomed to close 

 observation, and as based upon facts of undoubted significance, they 

 acquire a certain weight that entitles them to our confidence.^ 



In alleging a change of climate from the cutting off of woodlands, it 

 is not to be expected that a change will continue beyond the degree due 

 to the amount of clearing, and alter this is reached we might expect a 

 climate that would continue, on the general average alike, as long as 

 the amount of open country and of woodlands remained relatively the 

 same. Unfortunately, we have no records of rain-ftill or of tempera- 

 ture that show these phases cf climate as they existed when the country 

 "was covered with forest ; and the memory of the "oldest inhabitant" is 

 at best fallacious, unless sustained by circumstances which admit of 

 no doubt, as for instance, the freezing of rivers that does not now occur, 

 the culture of fruits now impossible, and facts of this kind which do not 

 simply depend upon opinions. 



It will be found that for more than a century the subject of climatic 

 effect from the clearing off of woodlands has engaged the attention of 

 observing persons, and there is good reason to believe that changes duo 

 to this cause may have occurred before their day from this cause, be- 

 cause these clearings had been extensive then, and in some cases there 

 have been no important clearings since the time when these observa- 

 tions were recorded.^ 



The occurrence of severe and protracted frosts, in a winter following 

 a dry autumn, has been found to be particularly injurious to trees, and 

 especially to fruit-trees. 



1 The spruce, one of the hardiest of trees in its proper climate, is found sensitive to 

 spring-frosts in the latitude of Paris. The Sequoia gigantea, planted at 1,250 meters 

 elevation, in Mduoire, France, after supporting the extreme rigors of several winters, 

 perished in October, 18C9, under an early aatumnal frost. 



The conifers of the Pacific coast are found unsuited to cultivation of many parts of 

 the Atlantic States where they might be expected a priori to be favorably located. In 

 their native region, they are accustomed to alternately wet and dry seasons, and after 

 a dry summer iu their new location, thty are found to start with a new growth in our 

 fall rains, only to be killed oil' by the frosts of the following winter. It is apparently 

 from the differences that prevail iu this respect, in our Rocky Mountains, that the coni- 

 fers from thence, as a rule, do better in the Atlantic States than those from California 

 and Oregon. In fact, the failure of the latter has come to be so general, that expe- 

 rienced nurserymen in the Atlantic States and Mississippi Valley have become quite 

 discouraged iu attempting to cultivate these trees, when brought from a region whore 

 the seasons are marked by a strong contrast of wet and dry weather. 



2 Upon this subject the reader is referred to the work by the Hon. George P. Marsh, 

 entitled " Man and Nature, or Physical Geography as Modified by Human Action " (18G4), 

 and to his later edition, entitled " The Earth as'Modified by Ruman Action," for a multi- 

 tude of facts bearing directly upon this subject. The titles which he quotes lead to a 

 very extended study of thin question. In citing from authors we have endeavored as 

 far as might be, to bring later evidences and facts not mentioned by him, presuming 

 that the reader who is carefully studying this subject, will avail himself of the informa- 

 tion which this author affords. 



^Kalm, who traveled in America in 1749, notices a supposed change of climate. 

 Volney, the French traveler, who visited our country toward the close of thu last 



