of the Radio-active Elements. 81 



In the above table the minerals can be divided into seven 

 general groups according to the localities from which they 

 were obtained, namely ; Group I from Connecticut (Nos. 1 to 

 9) ; Group II from North and South Carolina (Nos. 11 to 13) ; 

 Group III from Texas (Nos. 14 to 17) ; Group IV from Colo- 

 rado (Nos. 18 to 20) ; Group V from Norway (Nos. 21 to 35) ; 

 Group VI from Sweden (Nos. 36 and 37) ; Group VII from 

 Ceylon (Nos. 38 to 43). These groups can be further sub- 

 divided into Group I t from Glastonbury* and Group I 2 from 

 Branch ville, Group V, from localities in the neighborhood of 

 Moss (21 to 29) and Group V 2 from Arendal, and Group VII, 

 from the Sabaragamuwa Province and Group YII 2 from the 

 district of Galle. 



If the ratio of the lead to the uranium in these groups is 

 now considered, it is evident that in Group I, the average 

 value is 0*041 and the maximum divergence is less than five 

 per cent. In Group I 2 the average is 0*0535, which is in close 

 agreement with the four separate values given. In Group II 

 the agreement of the different values is not so good, but is 

 still very striking when the fact is taken into account that the 

 two specimens from North Carolina examined by Hillebrand 

 showed unmistakable evidence of slight secondary alteration 

 as did also the specimen from South Carolina, which moreover 

 is from a different locality and is placed with this group only 

 because there are no others with which to compare it. The 

 material used by the writer was to all appearances free from 

 alteration. 



In Group III an opportunity is afforded for the comparison 

 of different species from the same locality, for the yttrocrasite 

 described by Hidden and Warren was found only just across 

 the Colorado River from the famous Barringer Hill locality 

 which supplied the other Texas specimens. Here the agree- 

 ment of the ratios is again very satisfactory, especially in the 

 case of the yttrocrasite, which is one of the minerals the care- 



*I have been informed by Mr. E. B. Hurlburt of Glastonbury, Conn., 

 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 

 Hillebrand and described as from Glastonbury were actually foimd in that 

 place or even in the neighboring quarries of South Glastonbury. Colum- 

 bite, 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 collectors who afterwards obtained 

 the specimens. It is also equally possible that the specimens in many col- 

 lections labelled as from Middletown are also really from Portland. 



