May, 1885.] 



AND OOLOGIST. 



67 



Mississippi Valley except the extreme northern 

 part above LaCrosse. The temperature rose 

 throughout our district to 56° at St. Louis, and 

 35" at St. Paid, but north of there, beyond the 

 influence of the S.E. wind, fell rapidly to 18" at 

 Moorhead, and 11° at St. Vincent. The i.sotherm 

 of 40° is carried up to LaCrosse. A.s morning 

 approached the temperature still rose in the 

 northern part, and the sky became overcast, with 

 some local rain. It was a night of much migra- 

 tion, owing to the influence of the area of low 

 pressure, which at 7 a. m. , March 23d, was cen- 

 tral at Omaha and Yankton, (29.86 inches). Dur- 

 ing the next eight hours the pressure fell over the 

 wliole of the United States, the central point be- 

 ing still at Yankton, where the barometer at 3 p. 

 m., registered 39.74 inches. Here then was a 

 fall at Yankton of .33 inches during sixteen hours, 

 while the center of the low area moved but a few 

 miles; and the necessary result was a great rise in 

 temperature and consequently great movements 

 among birds. But these movements took place 

 only to the east of the low pressure area; for it is 

 a law of atmospheric circulation, that the winds 

 are attracted from the south, not directly toward 

 the centre of the low pressure area, but toward 

 places to the ednt of it toward which it is moving, 

 while the winds which it attracts from the north, 

 move toward places to the west or behind it. We 

 therefore would look in vain for migration to the 

 south, west or north of Yankton. The whole of 

 the immense movement, which in number of 

 records was as great as the three previous days 

 together, and in number of individuals was many 

 times greater, is to the southeast and east of 

 Yankton. We have said that the S.E., winds 

 prevailed up to LaCrosse, and this place also 

 marks the limit of the night's movement in that 

 direction. A map was made of the migration 

 which took place on this da}^ and it was found 

 to cover a very nearly circular area, two hundred 

 and fifty miles in diameter, whose center was 

 midway between Keokuk and Davenport. The 

 great number of birds which were migrating 

 during this night may be judged from the fact 

 that at St. Louis, twenty-six different species were 

 noted as having arrived or increased. It is well 

 to bear in mind that these birds were all migrating 

 on a rapidly falling barometer, hence in the face 

 of what is usually considered a sign of an ap- 

 proaching storm; and also we maj' notice tliat all 

 this great movement did not advance the van, 

 which still remained where it had been before. 



March 33d is a standstill. The area of low 

 pressure which was central at Yankton in the 

 afternoon of the'33d, had. by 11 p. ni., moved to 

 St. Paul, the barometer falling steadily to 29.61 



inches; during the night it moved N.E., to Mar- 

 quette, Mich., falling still more to 39,56 inches. 

 In the meantime an area of high pressure devel- 

 oped at Dodge City, Kans. The effect on the 

 winds was as follows: From St. Lo\iis south 

 ward the winds began to shift to S.W.; to the 

 northwest of that place they shifted to W., and 

 still farther north they became ]Sr.W.,andN. ; 

 while to the northeast of St. Louis they shifted to 

 S.W., and W. As would be expected, those 

 places that had W., and N.W., winds had clear 

 skies, while the district from St. Paul and La- 

 Crosse to Chicago and eastward was cloudy. 

 Temperature from St. Paul north, northwest and 

 northeast, rose; at St. Paul it was stationary, and 

 thence southward fell a few degrees, but still re- 

 mained warm. The wave of migration seems to 

 have exhausted Itself in a single night. Some 

 forty "firsts" are recorded for this day, but ex- 

 cept at two places they seem to have been ar- 

 rivals of the previous day which had been over- 

 looked. The two places, Waupaca, Wis., and 

 Heron Lake. Minn., with its neighborhood, fur- 

 nish one-half of the forty records, and are both 

 on the northern edge of the district covered by 

 the preceding night's migration. It seems, then, 

 that at these places there was a local, though in 

 the case of Heron Lake, a very large migration. 



March 34th is marked by cloudy weather after 

 a clear night. Southerly winds prevail over the 

 Upper Mississippi Valley, varying from S.E., to 

 S.W., and mostly light. The temperature has 

 fallen on an average 5° from Chicago to Bismarck 

 and northward. It has risen strongly, 9° to 11 ', 

 at Yankton and Omaha, this rise being probably 

 the cause of the arrival of immense numbers of 

 water fowl during the day, at Heron Lake, 

 Minn., all coming from the west, that is from the 

 direction of Yankton, at which place the wind 

 was S., at 7 a. m. It is a day of general low 

 pressure; the whole of the district from Cairo to 

 Moorhead is included between 39.80 and 29,89. 

 Northward the barometer falls to 29.65 at Mani- 

 toba; eastward to the same at Marquette, Mich. ; 

 southwest to 39.71 at Fort Smith, and westward 

 rises to 30.00 at Dead wood. An area of low 

 pressure developed at Fort Smith, Ark., in the 

 early evening of March 23d, and becomes pro- 

 nounced during the next twenty-four hours. At 

 7 a. m. to-day, the effect of this area is still hardly 

 felt, but by night Uie wind has been attracted to 

 it over most of the Upper Mississippi Valley, 

 bringing with it from the north, colder, clearer 

 weather. This day, then, is the turning day and 

 the beginning of a cold wave which is already 

 felt at the northwestward of Cheyenne. Tem- 



