1894 | NEW YORK ACADEMY OF SCIENCES. 145 
occurrences abroad ; but whether differential cooling or greater 
basicity in this portion of the magma perhaps developed accord- 
ing to Soret’s principle, or whether some more obscure cause 
primarily brought about the beginnings of the spheroids, are 
difficult questions. 
Search through the literature developed the following facts : 
Typical (7. e. biotite-muscovite) granites seldom develop sphe- 
roids. The Sardinian occurrence at Fonni, described by vom 
Rath* and Fouquéy is almost the only one yet noted. Several 
fine examples of these are in the Columbia College collections. 
They are larger than the Rhode Island nodules, Dut in general 
structure strongly resemble them. 
The usual spheroid bearing granite is either a biotite-granite 
(granitite) or a hornblende- -oranite. The former occurs in the 
Riesengebirge of Silesiay (described by Rose) and at Wirvik in 
Finland, as described by Frosterus§; the latter at Mullaghderg, 
in County Donegal, Ireland, as described by Hatch|| and at Slat- 
mossa in Sweden, as best and most recently set forth by Brég- 
ger and Bickstrom*]. The Wirvik spheroids resemble those 
described in this paper very closely, and the illustrative plates 
which accompany the descriptions are very like the one here 
given; but the outer radiating rim, so well developed in Rhode 
Island, is lacking. This radiating character also fails in almost 
all the Scandinavian examples, but at Mullaghderg it is even 
more pronounced than at Quonochontogue. Judging from the 
figure (Plate XVI., Fig. 1) of Dr. Hatch’s admirable paper, it 
forms a much larger portion of the nodule in the former case 
than in the latter. The radiating structure in a spheroid is most 
prominently shown in the orbicular diorite or corsite of Corsica. 
The spheroids are constructed of crystals of anorthite, which 
radiate from a center, and which are separated into concentric 
shells by layers of hornblende crystals. The parallel which they 
afford in a plutonic rock, to the spherulites of glassy rocks, so 
well discussed by Iddings** and Cross,++ is much closer than 
can be drawn from the cranitic nodules here discussed. 
* Sitzungsberichte d. Niederrhein. Gesellsch. in Bonn, June, 1885, p. 201. (As 
graced by Hatch, whose paper is later cited. The original is not accessible to 
emp.) 
+ Bull. Soc. Min. de France, x., p. 57, 1887. 
~G. Rose, Pogg. Annalen, Vol. LXI., p. 624. 
§ Tschermaks Min. und Pet. Mitth. XII1. 177, 1893—Plates VI. and VII. 
|| Quart. Journ. Geo. Soc., X LIV., 548, 1888. 
¥ Geol. Féren. i Stockholm, Férhandl. IX. 35]. 
gate J.P. Iddings—Spherulitic Crystallization. Bull. Phil. Soe. of Wash. XI. 445, 
tt WHitman Cross. Constitution and Origin of Spherulites in acid Eruptive 
Rocks. Idem, p. 411. 
