TBA.NS ACTIONS OF SECTION C. 657 



far into the air and subsequently fell to the o^round. One interesting point in con- 

 nection with earthquakes was the influence they had on wells and springs, and in 

 these respects the American earthquake had haci important results. Water now 

 stood where none occurred before, and in certain places springs had been dried. 

 The gas wells at Pittsburg were affected. It was too early yet to theorise on this 

 side of the Atlantic, but at present the earthquake seemed best explained by 

 referring it to some widely acting seismic disturbance, indications of which were 

 previously given by the geysers of the Yellowstone and by premonitory earthquakes 

 in South Carolina. It would probably be found, however, that its range and local 

 intensity had been controlled by the distribution of the rock masses, or by old lines 

 of earth movement and earth weakness. 



The following is a copy of Major Powell's telegram: — ' Earthquake most severe 

 on record in United States, and affected greatest area. Origin along line of post- 

 quaternary dislocation on eastern flanks of Appallachian, especially where it crosses 

 central North Carolina. Slight premonitory shocks in the Carolinas for several 

 days, moderately severe shocks occurring near Charleston, August 27 and 28. The 

 principal shock, causing great destruction in Charleston, originated in central North 

 Carolina, August 31, at 9.50 p.m. — 75 on meridian time. [2.50 a.m. September 1, 

 Greenwich time.] Thence the shock spread with great rapidity in aU directions, 

 with velocity varying from 25 to 65 miles a minute over area of 900,000 square 

 miles — one quarter of United States, from Gulf of Mexico to Great Lakes and 

 southern New England, and from Atlantic seaboard to Central Mississippi valley. 

 In the Carolinas it was accompanied by land-slides, crevasses, and great destruction 

 of property. Half of Charleston in ruins, and about 40 lives lost. No sea-wave yet 

 reported. A second moderately severe shock at Charleston, 8.25 a.m., September 1 ; 

 minor shocks followed at increasing intervals. The principal shock was felt over 

 this vast area in intervals of 15 minutes, and recorded at some principal points on 

 scale of intensity of 5 as follows: — Raleigh, 4, at 9.50 p.m.; Charleston, 5, at 9.54; 

 Cedar Keys [Florida], 2, at 10.05 ; Knoxville, 3, at 9.55 ; Memphis, 4, at 9.55 ; St. 

 Louis, 1-2, at 10.00 ; Milwaukee, 3, at 10.06 ; Pittsburg, 4, at 10.00 ; Albany, 2, 

 at 10.00; Springfield (Mass.), 1, at 10.00; New York, 2, at 9.53.' 



6. Sixth Report on the Volcanic Phenomena of Japan. 

 See Reports, p. 413. 



7. P,eport on the Volcanic Phenomeiia of Vesuvius and its neighhourhood. 



See Reports, p. 226. 



8. On the Seat of the Earth as influenced hy Conduction and Pressure. 

 By the Rev. A. Irving, B.Sc, B.A., F.G.8. 



The author, referring to the treatment of this subject by previous writers, in 

 particular Professors Green and Prestwich, draws attention to two physical con- 

 siderations of some importance, which appear to have been overlooked in the 

 discussion of the subject. 



1. In the case of a homogeneous sphere of uniform conductivity throughout, a 

 little consideration of the geometry of the sphere shows us that heat proceeding hj 

 conduction from the centre to the circumference must distribute itself through 

 spaces which increase in area by the square of the distance from the centre, that 

 the ' law of inverse squares ' in fact applies here to the intensity (temperature) of 

 heat so transmitted. It follows from this that if we take r = the radius of such a 

 sphere, and d = the distance of any point within the sphere from the centre, the 

 gradients of the curve for the increase of temperature with depth will be according 

 to the formula 



ir-d)^ 

 the temperature increasing as the squares of the depths. 



1886. U V 



