STARR — IOWA THUNDER-STORMS. 83 



The last obstacle to the best results is found in the fact that the 

 person superintending the work is not a professional meteorologist. He 

 has, however, a great desire to see Iowa thunder-storms carefully studied. 

 He believes it to be a subject that will repay diligent work; and if this 

 report, faulty though it be, may stimulate interest in the study, he will 

 be content. 



Three kinds of thunder-storms seem to be reported : 



First. Storms, well defined, traveling from the west, or a western 

 quarter, toward an eastern quarter. Time records, properly made, 

 supply data for calculating the rate of progress eastward. These are 

 apparently connected with the general atmospheric circulation of the 

 United States, and occur in the southeast quadrant of a "low" area. 



Second. Heat storms, local in character; not showing a progressive 

 movement; often unaccompanied by any wind ; seldom beginning until 

 well on in the afternoon, or in the evening. They accompany extreme 

 hot weather. 



Third. "Squalls," which are well characterized by Dr. Hinrichs in his 

 "Bulletins" for June and July, 1882. His account has been quoted by 

 others, but may again be copied here for Iowa readers : 



"Our Iowa squalls are as serious as any on the ocean; the wind 

 may be destructive, but it is not lifting nor revolving as it is in the 

 tornado. Roughly speaking, the squall may be likened to an extended 

 tornado, having its axis parallel to the ground. Here, in Iowa, it gener- 

 ally bursts upon us from the northwest, following the southeast wind; 

 it rolls over and strikes down upon us, usually with abundant precipi- 

 tation, and soon is succeeded by the same southeast wind which it so 

 abruptly displaced. * * So far as I have studied them, they come 

 down from the northwest, progressing at the rate of twenty to fifty 

 miles an hour. In Northeastern Iowa, the storm has a tendency to 

 bend up, so as to make the squall more nearly from the west. In like 

 manner, in Southwestern Iowa its front bends westward, and hence 

 blows more nearly from the north. The storm front is fierce in its 

 power along a considerable distance — twenty to fifty miles, and more, 

 in its front, along the earth, are struck simultaneously. As the great 

 storm-front moves on, it can be traced for 350 miles from northwest to 

 southeast through our State. It is impossible to confound this storm 

 with the tornado, which is fortunately very restricted in its field, mow- 

 ing a swath of destruction, generally, in a direction corresponding to 

 the line of the squall storm-front, from a southwesterly toward a north- 

 easterly point. The tornado is narrow, local; the squall at a given 



