OBSERVED IN WESTERN IOWA. 491 



sweeps rapidly southwards, gradually approaching the Appalachian mountains in Virginia, 

 but keeping east of thern, passes down around them in Georgia ; then turning abruptly 

 northwards it follows near their western base, crossing the Ohio not far from Cincinnati ; 

 thence running westerly passes near Springfield, 111., and, rising rapidly northwards as it 

 approaches the Mississippi, crosses that river near Rock Island ; thence in its westerly course 

 it makes a considerable and sudden bend to the south, rising north again in approaching the 

 Missouri, and continuing on apparently just north of this river till it reaches the sterile 

 plains. The line of 65° for the northern limit of the Alleghanian, nearly or quite coincides 

 with the limit assigned it by Prof. Verrill. 



Besides the shading together of contiguous faunae already referred to, there is a strag- 

 gling of representatives of certain species properly characteristic of one fauna through the 

 next one north, especially noticeable in several species of the Louisianian fauna, which not 

 infrequently reach New York, and occasionally Massachusetts. There is also a shading in 

 together of the Eastern and Western Provinces through the occurrence of several western 

 species on the prairies, which in general form their eastern limit, and a similar extension 

 westward, especially up the wooded valleys of the rivers, of species properly eastern. 



I. Western Iowa. 



Climatologicalky the prairies differ considerably from the States along the eastern sea-board, 

 on account of the adjoining wooded districts, and still more, their interior location. This 

 difference is most manifest in the more excessive extremes of heat and cold, moisture and 

 drought, and the greater prevalence of high winds. The summer, as a whole, is hotter, or 

 more tropical, 1 and the winter colder, though apparently the thermometric range is not much 

 greater than in the same latitudes eastwards. 2 The strong winds, which sometimes prevail 

 with great violence for days together, cannot but have some influence in determining the 

 particular character of the flora and fauna. In summer they render the great heat more 

 endurable, but in winter add greatly to the rigor of the climate, and at times render a 

 journey across even a comparatively narrow expanse of prairie extremely hazardous for 

 either man or beast. In addition to its ameliorating and intensifying effects, its mechanical 

 force alone is evidently not wholly without effect, especially upon sensitive species. 



Iowa being, as is well known, eminently a prairie State, we should expect, from the 

 scarcity of forest growth, an avi-fauna somewhat different from what exists in well-wooded 

 regions otherwise similar. And this we find to be the case ; the most marked differences 

 being the general scarcity of birds of all kinds, 3 the relative abundance of a few prairie- 



i The past summer I found in July and August the tempera- marked continental features at some seasons, and decided trop- 



ture for weeks together, during midday, ranging from 84" to ical features at others, and these influence the whole district 



96" F. I was at the same time assured that this was not an similarly, without showing any line of separation." L. 



unusual season. Blodgett, in Climatology of the United States (1857), p. 



a I am aware that this statement is somewhat at variance with 126. Compared with the wide climatic differences presented 



high authority on the Climatology of the United States. Mr. by the middle and western portions of our continent the dif- 



Blodgett, in remarking on the general character of the climate ference admitted may seem unimportant, in a general review 



east of the Rocky Mountains, observes: " The early distinction of the climates of a continent, yet they are of a sufficient 



between the Atlantic States and the Mississippi Valley has degree to become more or less prominent modifying influences 



been quite dropped, as the progress of observation has shown of faunae and floras. 



them to be essentially the same, or to differ in unimportant par- 3 The following extract from an entry in my journal under 



ticulars. It is difficult to designate any important fact entitling date of August 20, 18G7, after spending three days in the nar- 



them to separate classification; they are alike subject to great row belt of grand old timber skirting the Middle Coon, a few 



extremes and to the same extremes, they both have strongly miles above Redfield (Dallas Co.), quietly botanizing, but 



