Volcanic Disturbances in West Indies 287 



sand," marked "not of present erup- 

 tion." The sand has evidently been 

 washed by wave action, and nearly all 

 the lighter particles, feldspar and glassy 

 grovtndmass, removed, leaving the mag- 

 netite and hypersthene. A magnet 

 separates the brilliant black magnetic 

 grains from the more or less perfect 

 crystals and cleavage plates of hyper- 

 sthene. Most of the plates are of pris- 

 matic cleavage, but some are macropina- 

 coidal and show a bisectrix. Neither 

 hornblende nor augite were observed in 

 thesand. Its composition is remarkably 

 simple as compared with the auriferous 

 black sand of Oregon and California. 



In addition to the above, fragments of 

 old hypersthene andesite were obtained 

 at nine other localities. They will be 

 briefly noted, calling attention only to 

 points of difference as compared with 

 that already described. 



Among the ' ' building stones of St 

 Pierre, old rocks of the adjacent coun- 

 try " (6,7,8, and 11), there is but little 

 variation, and that chiefh' in the fine- 

 ness of the groundmass. One specimen 

 (8) differs from the others in containing 

 some augite and having a larger than 

 normal proportion of phenocrysts, prom- 

 inent crystals. Another No. 13) con- 

 tains a trace of deep-brown hornblende. 

 The two samples (Nos. 9 and 12) of 

 hypersthene andesite from near the bar- 

 racks, five miles north of Fort de France, 

 marked " old rock south of Pitons du 

 Carbet," are of the normal type. 



In three of the specimens of hyper- 

 sthene andesite considerable alteration 

 had taken place. No. 10, from " Font 

 St Denis, old rock between Pitons du 

 Carbet and Pelee," has no hypersthene. 

 Its place is occupied by a deep-green, 

 more or less fibrous, platy, pleochroic 

 mineral, with stronger birefringence 

 than ordinary chlorite. In No. 14, from 

 " Font St Denis, old rock covered with 

 new ash," the pyroxene is partly re- 

 placed by the chloritic mineral noted 

 above and surrounding calcite. 



A pebble (No. 3a) " from a ravine 

 on upper slope of plateau ' ' is hyper- 

 sthene, with a trace of augite and more 

 crystalline groundmass. The hyper- 

 sthene of the groundmass and some of 

 the larger particles have altered to a 

 yellowish-green product, in the coloring 

 of which oxide of iron may have played 

 a part. 



Hornblmde - hypersthene Andesites. — 

 These differ from the normal hyper- 

 sthene andesites in containing a small 

 amount of brown hornblende, which has 

 a narrow but dense black border. There 

 are no groups of pyroxene and magne- 

 tite to represent grains of hornblende 

 wholly resorbed, nor from the character 

 of the border here could such be ex- 

 pected. 



One specimen of this type (No. 15) oc- 

 curs ' ' near the barracks, five miles north 

 of Fortde France," and the hornblende 

 crystals in the hand specimen appear 

 prominent enough to place it among the 

 hornblende andesites, but in the section 

 under the microscope it most closely 

 resembles hypersthene andesite. An- 

 other (No. 5) is from St Pierre. It 

 varies from the normal hypersthene an- 

 desite not only in containing a trace of 

 hornblende, but also a grain of olivine, 

 the only one found in Mr Hill's collec- 

 tion from Martinique. A good speci- 

 men (No. 2) is " old rock from Fuma- 

 role Island, mouth of Riviere Blanches, ' ' 

 with dark felty groundmass, like many 

 of the typical hypersthene andesites. 



Hornblende Andesite. — The horn- 

 blende andesite is of a light gray color 

 and decidedly porphyritic even to the 

 unaided eye, with conspicuous black 

 crystals chiefly of hornblende, attaining 

 in a few cases a length of five milli- 

 meters. The white or glassy crystals 

 of feldspar are less prominent, and all 

 are imbedded in a light-gray ground- 

 mass. Under the microscope hyper- 

 sthene and magnetite and also the 

 plagioclase are seen to occur as in the 

 hypersthene andesites, but less abun- 



