Catnpton'itc Dikes, Etc. — Marsters. 99 
correspond and tlu-. extinction for each occurs at a diflerent 
point. It would seem from tliis that the small basaltic horn- 
blende crystals were first to form and that they then became 
involved in the large augite crystals whose period of genera- 
tion marks a later stage. 
The close intermingling and association of hornblende and 
augite constitute one of tiie most interesting and striking 
features of many rocks. The relations of the two have often 
led to the conclusion that the hornblende had resulted by 
paramoridiism from original augite. Hawcs,' Irving,^ Van- 
Hise,' Williams/ Herrick,'' Hobbs,'' Lawson," and G. F. Rich- 
ards,^ have remarked it in this country and such conclu- 
sions seem the ones generally to be drawn. Less often the 
two are related as in the present instance, in which the horn- 
blende is undoubtedly of older age than the augite and has 
been afterward taken up in its mass. Teall ^ has noted this in 
England, and the senior author '^ of the present paper previ- 
ously in this country. 
In addition to the above mentioned porphyritic crystals of 
augite (which range from 0.5 m.m. to 15 or 20 m.m.) are 
found other irregular masses of the same mineral. These 
present no crystallographic outline and were doubtless formed 
by a second generation later than the porphyritic type. In 
both, included magnetite occurs in small octahedra. 
The hornblende is the most abundant and most character- 
istic component of the rock. It exhibits minute rod-shaped 
crystals 0.1 m.m. broad by 0.5 m.m. long, of the basaltic 
type. Although the faces of the prism zone are well developed 
as shown by frequent cross sections, the terminal faces are 
lacking. Their fractured condition is probably due to move- 
' G. W. Hawes, Geol. of N. H., vol. hi, pp. 67 and 206, pi. vii, fig. 1. 
- R. D. Irving, Geol. of !»'«>., vol. in, p. 170. 
'C. R. VanHise, Am.' Jour. Sci. (in) xxvi, 29. 
*G. n. Williams, Am. Jour. Sci. (iii) xxviii, 259. In this paper will 
be found also many references to occurrences of the same phenomena 
abroad. 
^C. L. Herrick, Bull, of Lab. of Denison Univ., (Granville, O., vol. 
II, p. 1.30. 
* W. H. Hobbs, Bull. Mus. Comp. Zool., Harvard, Univ., vol. xvi, 
No. 1, n. 10. 
'A. C. Lawson, Proc. Can. Inst., Toronto, Apr., 1888, p. 176; also 
Amer. Geol., Apr. 1SH8. 
"G. F. Richards, Bull. Denigon Unir., vol. iv, p. 6. 
M. .1. H. Teall, Quart. Jour. Geol. Soc, vol. 40. p. 653. 
'".I. F. Kemp, Am. Jour. Sci. (iii) xxxvi, p. 250. 
