October 18, 1007] 



SCIENCE 



519 



Simplon are: (a) The Jura-Trias sediments, 

 lithologically often much alike and much in- 

 terfolded; (b) the Paleozoic crystalline schists ; 

 and (c) the gneiss of Monte Leone and the 

 Antigorio gneiss, both stated to be of Archsan 

 age. These rocks throughout contain radium, 

 and for the most part in quantities much 

 above what hitherto has been ascribed to sedi- 

 mentary or igneous rocks. 



Some thirty-six typical samples, taken from 

 various points in the tunnel, have been ex- 

 amined. The poorest in radium are certain 

 anhydrite rocks. Certain amphibolite schists 

 go very high. The Antigorio gneiss rises 

 from 10.5 X lO"'^ and 8.0 X 10"" grams radiiun 

 per gram of rock at the Italian entrance to 

 23.7 X 10-*= at 4,000 meters inwards. Some of 

 the Archaean gneisses yielded very high results. 

 Such quantities of radium if generally dis- 

 tributed throughout the rocks of the massif 

 would be suiEcient to disturb any forecast of 

 the temperature which under normal condi- 

 tions would be encountered at the level of the 

 tunnel. It is suggested that the radium was 

 in fact the source of the discrepancy between 

 the predicted and the observed rock tempera- 

 tures. 



As it is improbable that these results are 

 unique and apply only to this particular sedi- 

 mentary accumulation and locality, they ap- 

 pear to point to hitherto unsuspected quanti- 

 ties of radium (and its parent elements) in 

 the immediate surface materials of the earth. 

 It seems impossible to avoid the conclusion 

 that these elements were precipitated along 

 with the sediments entering into the composi- 

 tion of the massif. The question then arises 

 whether the accumulation of such quantities 

 ■or radioactive elements may not enter as a 

 factor in the events attending mountain-build- 

 ing. It can be shown that an area of sedi- 

 mentation whereon has been accumulated some 

 10,000 meters of sediments, having a richness 

 in radium comparable with the Simplon rocks, 

 must necessarily become an area of greatly 

 lessened crust-rigidity, and would hence be- 

 come the probable site of crust-flexure under 

 tangential compressive stress. 



Further investigation will be required be- 



fore such views can be generalized and the 

 importance of radium as a source of in- 

 stability of the earth's crust be determined. 

 Apart from any speculations as to the influ- 

 ence of radium as the cause of an energetic 

 substratum, the shifting of radium and its 

 parent elements by denudation must be re- 

 garded as a convection of thermal energy, and 

 this convection, if the quantities involved 

 are sufficient, must, under the conditions re- 

 ferred to above and the unceasing action of 

 denudation, become rhythmic in operation, and 

 at the same time must result in shifting the 

 areas of high temperature and crust-weakness 

 from age to age as the site of sedimentary 

 accumulation changes. J. Joly 



THE ARC OF PERU 



The Committee of the French Academy of 

 Sciences having scientific control of the 

 French Geodetic operations on the equator 

 has reported the completion of the remeasure- 

 ment of the historic arc of Peru.* 



This arc was measured by the French 

 (1736-1743) and used in connection with a 

 similar arc in the Arctic regions, also meas- 

 ured by the French, to decide a question in 

 regard to the form of the earth which had 

 arisen as the result of Cassini's surveys in 

 France. 



A discussion of the measurement of the arc 

 can be found in the report of the Superin- 

 tendent of the Coast and Geodetic Survey for 

 1889, appendix 7. 



In 1889, the question of remeasuring this 

 arc was brought before the International Geo- 

 detic Association by the Delegate of the 

 United States, Professor George Davidson, 

 who suggested that France should have the 

 prior right to execute the work. 



Circumstances prevented any active work 

 until 1898, when the discussion of the subject 

 was renewed in the same association as the 

 result of a motion offered by the Delegate of 

 the United States, Mr. E. D. Preston. The 

 association voted in favor of the proposition 

 to remeasure the are and the French delegates 

 undertook to have the work done. 



' Comptes Rendus EeMcmiadaires des Seances 

 de L'Acad4niie des Sciences, No. 6, 5 Aotlt, 1907. 



