8()0 J. BARRELL MEASUREMENTS OF GEOLOCJIC TIME 



that the only alterations which would affect the matter must involve the addi- 

 tion or abstraction of uranium or lead, and mere hydration, for example, should 

 be without effect. The nivenite, interpreted by the rule, indicates an age fifty 

 times as great gis seems admissible from a geological standpoint and four times 

 as great as the Glastonbury mineral, which would seem on geological grounds 

 nearly coeval with it. 



"I find no convincing evidence that the law of decay is so simple as is as- 

 sumed. Under the conditions in which uranium compounds are stable, \ must 

 necessarily reduce to zero. It is in the highest degree probable that X is a dis- 

 continuous function, and it is to the same degree probable that the law of decay 

 fails like Boyle's law, or that X varies with circumstances, such as may have 

 environed a mineral in a pegmatite, even though heat alone or pressure alone 

 may be without effect upon radioactivity. 



"It does not seem to me that geologists can possibly accept the ages of min- 

 erals as determined from the uranium-helium or the uranium-lead ratios, which 

 do not seem consistent and are far longer than stratigraphers could admit." "^ 



GEOLOGICAL EVIDENCES OF AGE OF URANIUM MINERALS 



Upper Paleozoic age of Glastonbury uraninites. — In reviewing Becker's 

 statements the relative ages of the uranium minerals from the Glaston- 

 bury and Barringer Hill localities should be given first attention. It will 

 be seen that the age ascribed to each is quite clearly in error. and that 

 their relative ages are very different. 



In regard to the location and age of the Glastonbury uranium minerals, 

 Hillebrand in 1890 ascribes them to Hale's quarry, but Becker overlooks 

 the statement which Boltwood makes in the article which forms the basis 

 of Becker's discussion. Boltwood states : 



"I have been informed by Mr. E. B. Hurlburt, of Glastonbury, Connecticut, 

 who has made a careful study of the mineral occurrences in his locality, that 

 he considers it to be highly improbable that the specimens examined by Hille- 

 brand and described as from Glastonbury were actually found in that place, or 

 even in the neighboring quarries of South Glastonbury. Columbite, monazite, 

 a mineral resembling polycrase, and autunite are found at South Glastonbury ; 

 but Mr. Hurlburt, who has looked into the matter quite thoroughly, is of the 

 opinion that the specimens of uraninite credited to Glastonbury must have been 

 found in the feldspar quarries of Portland, a town on the east bank of the 

 Connecticut River between South Glastonbury and Middletown. A number of 

 years ago uraninite in some quantity was found at Portland, and as some of 

 the workmen in the Portland quarries had their homes in South Glastonbury, 

 its occurrence in the latter locality may readily have been assumed by the col 

 lectors who afterward obtained the specimens. It is also equally possible that 

 the specimens in many collections labeled as from Middletown are also really 

 from Portland." "^ 



111 Relations of activity to cosmogony and geology, loc. cit., 1908, pp. 133-1.35. 



"2 B. B. Boltwood : On the ultimate disintegration products of the radioactive ele- 

 ments. Part II, — The disintegration products of uranium. Am, Jour. Sci., vol. xxiii, 

 X907, pp. 77-88 ; see p. 81. 



