January 2, 1885.] 



SCIENCE, 



13 



settlement of the western portion of Kansas will 

 have a similar effect upon its rainfall; but it is not 

 reasonable to expect that western Kansas will ever 

 boast of a rainfall equal to that of eastern Kansas. 

 So long as the eastern half of the state remains to 

 the east of the meridian forming the western bound- 

 ary of the Gulf of Mexico, the south winds will cause 

 it to receive much larger supplies of vapor, for con- 

 densation into rain, than will be received by the 

 western half of the state, which lies beyond the im- 

 mediate track of the vapor-laden winds. It must be 

 remembered that climatic changes are exceedingly 

 gradual; and a rain deficiency or excess for a single 

 year, or for two or three years in succession, must not 

 be considered as invalidating the law of general 

 averages. Neither should the fact that the rainfall, 

 upon the whole, is increasing, induce settlers to break 

 land in the western third of Kansas with the expec- 

 tation of successfully raising the same crops as in 

 eastern Kansas. Such settlers will surely be disap- 

 pointed. It is even doubtful if paying crops of any 

 kind can ever be continuously produced in that region. 

 With an average before settlement of about fifteen 

 inches per annum, the same percentage of increase 

 as has been made in eastern Kansas in thirty years 

 would give an annual amount of less than eighteen 

 inches, — a quantity entirely inadequate to maintain 

 successful agriculture. 



AMERICAN SOCIETY FOR PSYCHICAL 

 RESEARCH. 



At a meeting held in Boston, Sept 23, to consider 

 the advisability of the formation of a society for 

 psychical research in America, the whole matter was 

 placed in the hands of a committee of nine, consist- 

 ing of Dr. G. Stanley Hall of Johns Hopkins univer- 

 sity; Prof. E. C. Pickering, director of the Harvard 

 college observatory; Dr. H. P. Bowditch and Dr. C. 

 S. Minot, of the Harvard medical school; Mr. S. H. 

 Scudder, president, and Professor Alpheus Hyatt, 

 curator, of the Boston society of natural history; Pro- 

 fessor William James of Harvard college; Profes- 

 sor William Watson of Boston ; and Mr. N. D. C. 

 Hodges of Cambridge. This committee held a num- 

 ber of meetings during the months of October and 

 November, and issued an invitation to a number of 

 scientific men throughout the country to join in a 

 society under a constitution upon which they had 

 decided. To this invitation there were favorable 

 replies from about eighty. 



The first meeting of the society was held in Boston 

 on the 18th of December. Under the constitution 

 the conduct of the society is placed in the hands of a 

 council of twenty-one, seven to be chosen each year, 

 to hold office three years. Of this council, there were 

 elected at this first meeting, fifteen : Prof. G. Stanley 

 Hall, Prof. George S. Fullerton, Dr. William James, 

 Prof. E. C. Pickering, for three years ; Professor Simon 

 Newcomb, Dr. C. S. Minot, Dr. H. P. Bowditch, 

 Mr. X. D. C. Hodges, for two years ; Prof. George F. 

 Barker, Mr. S. H. Scudder, Rev. C. C. Everett, Mr. 



Morcfield Storey, Professor John Trowbridge, Profes- 

 sor William Watson, Professor Alpheus Hyatt, for 

 one year. 



The sub-committee on work made an informal 

 report, and has since issued a circular to members, 

 asking for volunteers on the investigating committees 

 and for information regarding promising subjects for 

 investigation, such as mediums, mind-readers, mes- 

 meric subjects, etc. 



The society adjourned to meet on the ninth day of 

 January. 



THE NATURAL BRIDGE OF VIRGINIA. 1 



During a recent trip to Virginia (Oct. 2 to 6) I 

 visited the Natural Bridge ; and although in posses- 

 sion of the guide-book of the locality (edition of 

 1884), and the admirable articles published by Major 

 Jed. Hotchkiss in The Virginias, I failed to obtain 

 certain information relating to the bridge, which 

 would be of special interest to the topographer and 

 geologist. Some of the observations which I made, 

 although of a general character, may be of interest. 



The bridge is undoubtedly the remnant of the top 

 of a cave which was probably formed long before the 

 Luray cavern, which is excavated out of the same 

 lower Silurian limestone formation. The bridge 

 seems to be located in the centre of a gentle basin or 

 synclinal in the strata, which may account for the 

 roof of the ancient cavern being left at this special 

 point. The height of the bridge has evidently been 

 much augmented by a lowering of the bed of Cedar 

 Creek through the agency of chemical and mechanical 

 erosion after the destruction of the original cavern. 

 The height of the original cavity, at the point where 

 the bridge now exists, was in consequence very much 

 less than the present height of the intrados of the 

 bridge-arch. 



The elevation of the railroad-track at Natural- 

 Bridge station, on the Shenandoah valley railroad, is 

 seven hundred and sixty feet above ocean-level; and 

 the elevation of Cedar Creek, under the north face of 

 the bridge-arch, is nine hundred and fifteen feet, as 

 determined by two independent lines of barometric 

 levels which I ran between the railroad-station and 

 the bridge. 



The height of the crown of the arch on the north 

 side, at the ' Lookout Point,' is one hundred and 

 eighty-eight feet above the creek, measured with a 

 cotton twine, which was the only line of the required 

 length which could be obtained. The same height 

 measured by the barometer (Short & Mason aluminum 

 aneroid) was determined as one hundred and eighty- 

 six feet. Neither of these methods of measurement 

 is sufficiently exact to permit of a final statement, 

 but the results are of interest in the absence of more 

 definite data. 



The thickness of the arch under the crown on the 

 north side is approximately forty-six feet, and on the 

 south side thirty-six feet. 



3 Read before the American philosophical society, Oct. 17. 

 1884, by Charles A. A*hruknek. 



