228 SPARKS FROM A GEOLOGIST'S HAMMER. 



to minus 30 at Milwaukee, but only reached minus 14 

 at Northport and Traverse City. At the same time it 

 was minus 29 at Chicago and minus 20 at Kalamazoo. 

 It sank to minus 24 at Saint Louis and minus 16 at 

 Memphis, Tennessee. This point was two degrees colder 

 than Northport, 640 miles farther north in a direct line. 

 The isotherm of minus 24 bends from the latitude of 

 Alpena, through Grand Rapids, Battle Creek and Cold- 

 water, and thence to Saint Louis, 452 miles farther south. 

 Cincinnati is reported to have an extreme minimum of 

 minus 29, a degree of cold not known in the peninsula 

 of Michigan, and but little exceeded along the south shore 

 of Lake Superior. At Ann Arbor the lowest point reached 

 in twenty-eight years is minus 24. On January 1, 1864, 

 it was minus 18 at Ann Arbor. The area of the ex- 

 treme minimum of minus 24 seems to cover all the 

 central portion of the peninsula east of Grand Rapids, 

 west of Bay City, and south of Otsego Lake, and stretches 

 southward into central Kentucky. Compared with Trav- 

 erse City, the extreme minimum of Hazelwood, Minnesota, 

 is 22 lower; that of St. Johnsbury, Vermont, 28 lower; 

 that of Gardiner, Maine, within thirty miles of the ocean, 

 19 lower, and of Montreal 26 lower. 



A few more specific illustrations may be added. On 

 the 18th of November, 1880, while the thermometer was 

 5 at Milwaukee, it stood at 18 at Grand Haven and at 

 10 at Port Huron. At the same time it was 8 at Saint 

 Louis, 2 at Denver, 4 at Dodge City, Kansas, and 6 as 

 far south as Fort Gibson, Indian Territory. On the 19th 

 of November, while the thermometer marked 29 at Grand 

 Haven, it was 13 at Port Huron ; and farther south it 

 marked 14 at Chicago, 2 at Indianapolis, 11 at Louis- 



