39-i Scientific Intelligence. 



surface characteristic of massive rocks and absent from rocks 

 traversed by systems of joints. 



The extent of the granite body is not less than 10 miles in one 

 direction by 3 miles or more in the transverse direction. Uni- 

 formity of character through such an area affords reasonable 

 presumption that uniformity will be found in the vertical direc- 

 tion to such depths as are obtainable by the driller. The age of 

 the batholith is not definitely known, but it is believed by stu- 

 dents of Georgia geology to be probably pre-Paleozoic, and cer- 

 tainly not later than early Paleozoic. Of the later geologic 

 history all that is demonstrated by the features of the locality is 

 profound degradation, resulting in the development of a broad 

 peneplain. Nothing is known in the vicinity of later orogenic or 

 volcanic events, and the Cretaceous and Tertiary formations of 

 the Coastal Plain are thought not to have covered this area. So 

 far as is known, the region is one characterized by prolonged 

 geologic quiet, and it has probably been exempt, as far as any 

 locality which might have been selected in the United States, 

 from physical and climatic accidents competent to disturb the 

 arrangement of subterranean temperatures." 



Besides the actual determination of the temperature-gradient, 

 the conditions will be favorable for the prosecution of other 

 investigations. The study of the core obtained would give valu- 

 able data as to the strength and physical properties of deeply 

 buried granite. Further : 



" It is at least worthy of suggestion that the boring could also 

 be utilized for the subterranean swinging of a specially con- 

 structed pendulum, and the measurement of the earth's weight by 

 means of a vertical pair of gravity determinations could thus.be 

 repeated. The homogeneity of the crust layer between the 

 upper and lower stations and the representative character of the 

 rock samples brought up as drill cores would be peculiarly favor- 

 able for the determination of the density of the crust layer. 



To give high precision to the determination of density it 

 would be necessary to take account of the compression of the 

 rock under stress of the superincumbent weight. Rock com- 

 pression has not yet been measured in the laboratory, the matter 

 being one of extreme difficulty, by reason of the deformation of 

 both samples and testing apparatus when great pressures are 

 applied ; but there is reason to think that valuable observations 

 bearing on this point could be made within the boring at some 

 stage of the work. It should be possible, by suitable automatic 

 appliances, to measure that resilient elongation of the column of 

 rock constituting a section of core which theoretically takes place 

 while the drill is separating it from the general mass. The 

 importance to geophysics of experimental determinations of rock 

 compression is generally recognized." 



It is much to be hoped that it may prove possible to go for- 

 ward with this most important investigation. The expense 

 would be large, of course, but for a depth of 6000 feet not pro- 

 hibitory ; one estimate puts the cost of the boring at $110,000. 



