528 PROCEEDINGS OF THE AMERICAN ACADEMY. 



3 G. Rose, Pogg. Ann., IX. 206, 1827. 



4 H. Baumliauer, Zeit. f. Kryst., 18, 31, 1890. 



5 Hoskyns-Abrahall (Inaug. Diss. 1889), Abs. Zeit. f. Kryst., 21, 389. 

 e Heusser, Pogg. Ann., 87, 468, 1854. 



7 K. Zimanyi, Zeit. f. Kryst., 22, 331, 189-3. 



8 Schrauf, Ber. Acad. Wien, 62 (2), 745, 1870. 



9 " " " " 42, 111, 1862. 



10 Carnot, Bull. Soc. Franc. Mineral., 19, 135, 1896. 



11 Flink, Bihang t. K. Sv. Vet. Aliad. H. Stockholm, 12 (2) No. 2, 42, 1886. 



12 Schmidt, Zeit. f. Kryst., 7, 551, 1883. 



13 Hidden & Washington, Zeit. f. Kryst, 14, 299, 1888. 



14 Jeremejew & Nikolajew, Zeit. f. Kryst., 11, 389, 1886. 



15 Vrba, Zeit. f. Kryst., 15, 464, 1889. 



16 Artini, Rendic. R. Ace. Lincei, Roma, 4 (2), 259, 1895. 



17 Sandberger (Hilger), N. J. Min. 1885, 1, 171. 



18 Pusyrewsky, Verb. k. k. Mineral. Gesell. St. Petersburg, 1859-1860 (cited 

 by Baumhauer, No. 4 above). 



19 Latterman, Rosenbusch, Mik. Phys., I. 409, 1892. 

 WeibuU, Gcol. For. Forh., Stockholm, 20, 63, 1898. 



^^ } " " " " " 8, 492, 1886. 



One point brought out by the preparation of this table is the lack of 

 studies of apatite in which on the same material all these characters have 

 been determined. It is also to be noted that no crystallographic data 

 whatever appear to have been secured on what could fairly be called a 

 chlor-apatite, the highest chlorine content in the table being about 0.5 

 per cent only. Without such data it does not seem that the theory of 

 Pusyrewsky and Baumhauer that axial ratio decreases with chlorine 

 content can be considered as established. Moreover exceptions to that 

 rule may be noted in the table, notably Nos. 5, Zillerthal, and 9, 

 Jumilla. On the other hand it seems fairly safe to accept the statement 

 that an apatite with large angle c to x (40° 17' or more) will be 

 practically free from chlorine. 



The table shows that absolutely no definite relation exi.sts between 

 the specific gravity and the chlorine content. Nos. 2 and 9, from 

 Achraatowsk and Jumilla, having about 0.5 per cent chlorine, have 

 specific gravity respectively 3.12 and 3.235 ; while the chlorine-free 

 varieties have specific gravities from 3.09 to 3.22, or practically the 

 same range. Observations on the birefringence are few, but so far as 

 they go do not point to a definite relation to the chlorine content. 



Harvard Mineralogical Laboratory, 

 December, 1901. 



^ 



