39 



to Ogdensburg and Flattsburg, and strikes the ocean at Portland, Maine, 

 being considerably bent south by the mountains of Vermont and New Hamp- 

 shire. 



Whoever shall take his map of the state, and trace these isotherms, will 

 perceive that they have crossed each other at or near Portage City where 

 the govermental observations were taken some years since, from which one 

 element of them has been calculated : that the winter and fall isotherms 

 are almost at ri'ght angles to those of the summer and spring, and are almost 

 equally varying from the mean annual line, but on opposite sides. 



From what we have been able to gather, we think we have discovered, 

 that near the center of Wisconsin there exists an axis extending from some- 

 where near Plover, in Portage county, south into the stateof Illinois, along 

 which, at different seasons of the year, sharp curves in the isotherms are 

 made to vibrate, and that along the same axis coQsiderab.'« change takes 

 place in the amount of water fall during the year. 



The isotherms that most effect vegetation, are those of TO degirees in sum- 

 mer, and 20 in winter — the on« operating upon the growth of vegetation 

 and the productien of annuals ; the other destroying many perennials which 

 survive in other places on the annual isotherm. The first allows the variety 

 of cori', melons and other summer annuals grown in central Ohio and southern 

 Pennsylvania to perfect in southern Wiscopsin ; while the second is fatal upon 

 all the /tender trees, such as pears and peaches. 



Those who have hereto''ore lived where the isotherm.'!, at different seasons 

 of the year, ran in nearly or quite paralel lines, might be readily mistaken 

 in the climate of Wisconsin, by knowing the winter or summer tempei^ature, 

 and comparing that with the same temperature in his native place. Such 

 persons might meet with as fatal results as would the man from this state, 

 who, having only a knowledge of the winter temperature of Ireland or England, 

 should plant h'S field with corn, and expect a harvest of ears ; or that of th« 

 man from Newfoundland, who having no knowledge of Wisconsin tempera- 

 ture, except of winter in Columbia county, should refuse to plant corn or 

 cucumbers, because he thinks they would not grow by reason of such cold 

 in summer as he had been accustomed to experience. 



From the fact, that the high temperature of summer, forces forward a 

 growth, and the dry atmosphere induces perfection in the new wood, early in 

 the fall, it may safely be expected, that those trees, which thrive along the 

 annual isotherm east of us, will survive the colder temperature of our winters, 

 and especially, if we shall afford such trees the shelter of others which have 

 proved themselves hardy ; for a similar reason, we may expect trees, from 

 colder mean temperatures, to take up their abode in the southern counties, if 

 sheltered from the hot winds. Hence, we have been induced to recommend 

 several trees, not natives of the state, for cultivation, as the chestnut, tulip, 

 some species of the hickory and the European walnut, and also of the white 



