Febeuary 8, 1907] 



SCIENCE 



227 



spring has long been known and is much 

 frequented by tourists visiting Chattanooga. 

 It may be reached by the Alton Park electric 

 cars, or by the Chattanooga Southern Eail- 

 way. The proximity of the spring to Chat- 

 tanooga and its accessibility has doubtless 

 added much to its notoriety. 



In general appearance the spring is not 

 unlike many other bold springs met with 

 along the eastern base of Lookout Mountain. 

 It flows from a fissure, at the base of a lime- 

 stone bluff, forming a good-sized stream. The 

 spring itself reveals but little evidence of the 

 phenomenon for which it is noted. Neverthe- 

 less, the phenomenon can readily be detected 

 by holding a smoldering match or lighted 

 paper near the opening from which the water 

 flows. The motion of the air is to be seen in 

 its full force at an opening in the bluff above, 

 about forty feet distant, and at an elevation 

 of ten or fifteen feet above the spring. At 

 tiis opening, which leads down to the stream 

 supplying the spring, there is, at times, a 

 strong current of air passing inward or out- 

 ward, depending on the atmospheric condi- 

 tions hereafter to be discussed. The writer 

 was informed by Mr. W. H. Grant, the present 

 owner of the spring, that the opening above 

 referred to was formerly of sufficient size to 

 admit the body of a man; and furthermore, 

 that he, together with a civil engineer, some 

 years ago entered the opening which led into 

 a cave having large chambers fifteen feet or 

 more in height. The distance to which the 

 cave was explored by Mr. Grant and his com- 

 panion was not measured, but it was estimated 

 to be nearly a mile. The direction of the 

 cave is said to be southward parallel with 

 Lookout Mountain. Mr. Grant reported that 

 they noticed no current of air in the cave. 

 This, however, may be accounted for by their 

 using a lantern which would not be affected 

 except by a strong draught. The stream 

 forming the spring was found traversing the 

 cave as far as the exploration extended, and 

 many stalactites and stalagmites were reported 

 in the larger chambers. 



The formation in which the cave occurs, 

 and from which the spring flows, is one of the 



lower members of the Carboniferous rocks 

 known as the Bangor limestone. It consists 

 of a very pure heavy-bedded blue or grey lime- 

 stone attaining a thickness, in the neighbor- 

 hood of Chattanooga, of about 800 feet. In 

 the immediate vicinity of the blowing spring, 

 the formation dips at a low angle westward 

 toward the axis of Lookout Mountain. The 

 Bangor limestone is highly soluble in meteoric 

 waters and frequently gives rise to limestone 

 sinks and caves of greater or less extent. 



At the writer's suggestion, Mr. Grant made 

 a series of observations on the blowing spring 

 in order to determine the time and direction 

 of the air currents, together with the relative 

 temperature of the water flowing from the 

 spring and the outside air. The results of 

 the observations, which extended from De- 

 cember 21 to December 26 inclusive, are em- 

 bodied in the following table: 



The following barometric readings fur- 

 nished by Mr. L. M. Tindell, officer in charge, 

 U. S. Weather Bureau, Chattanooga, Tenn., 

 show the variations of the atmosphere pres- 

 sure during the time of Mr. Grant's observa- 

 tions. 



The tables here given will be further con- 

 sidered at the end of this paper in the dis- 

 cussion of the explanation of blowing springs 

 and wells. 



