58 Expedition to the 



try generally, abounds in sink holes sometimes of great depth. 

 These are very numerous, from five to seven miles back 

 of the town. They are in the form of vast funnels, having 

 at the surface, a diameter of from twenty to fifty yards. 

 Mr. Say descended into one of these, for the purpose of as- 

 certaining the medium temperature below the surface of 

 the earth. This sink opens at the bottom of a deep ravine. 

 It has two apertures near each other, through which water 

 is admitted, and each large enough to afford passage to the 

 body of a man. Within are two chambers from six to twelve 

 feet in breadth, and thirty-five feet long. At the bottom of 

 the second chamber, is a pool of water rather difficult of ac- 

 cess. In this apartment the Mercury stood at 60° Fah. : in 

 a shady part of the ravine about twenty-five feet below the 

 general surface at 75°. The grassy plains to the west of 

 St. Louis, are ornamented with many beautifully flowering 

 herbaceous plants. Among those collected there, Dr. Bald- 

 win observed the aristolochia Sipho, cypripedium specta- 

 bile,* lilium catesbeiana. bartsia coocinnea, triosteum per- 

 foliatum, cistus canadensis, clematis viorna, and the trades- 

 cantia virginica. The borders of this plain begin to be over- 

 run with a humble growth of black jack and the witch hazle,f 

 it abounds in rivulets, and some excellent springs of water, 

 near one of which was found a new and beautiful species of 

 viburnum. On the western borders of this prairie, are some 

 fine farms. It is here that Mr. John Bradbury, so long and 

 so advantageously known as a botanist, and by his travels 

 into the interior of America, is preparing to erect his habi- 

 tation. This amiable gentleman lost no opportunity during 

 our stay at St. Louis, to make our residence there agreeable 

 to us. Near the site selected for his house is a mineral 

 spring, whose waters are strongly impregnated with sulphu- 

 retted hydrogen gas. Cattle and horses which range here 



* C. parviflorum? f Hamamelis virginica, and quercus nigra. 



