PALLASITE. — CUMIiKKLANDITK. 70 



the porphyritic feldspar portion, so far as the writer has ohserved. The structure of this 

 section is shown in Plate T. figure 6. In this the struelure of the altered fissured olivine, 

 closely resembling the olivine of figure 5, is clearly shown. 



No. 1003 shows more serpentine characters than No. 1001, having less iron and 

 more of the irregular serpentine masses. In the section tiie characUirs are essentially 

 the same as those of No. 1001. Some talc in fine scales aggregated together was seen 

 towards the interior of the larger serpentinized olivines, and in the macro.scopically visi- 

 ble serpentine masses before mentioned. The serpentine in these masses is pale-gTe<.*u 

 and isotropic. The serpentine replacing the olivine shows the .same fibrous charact'^r 

 as No. 1001, but the structure is better marked, and the fibrous plates polariztuJ with 

 brilliant colors. In portions of the section considerable actinolite was observed. 



Nos. 1004, 1009, 1010, and 1011 are from the side of the hill opposite to No. 

 1000, and with the preceding specimens show the gradual change from one si<le, on 

 which is to be found such material as No. 1000, to tho.se masses which have suHered 

 very great alteration. Part show ochery patches of ferruginous alteration. In general, 

 the sponge-like structure of the magnetite still remains, and besides this the inters];aces 

 are variously filled with talc, serpentine, actinolite, etc. — the serpentinous material pre- 

 dominating over the others. Owing to the extreme alteration, some of these specimens 

 have developed an imperfect fissile or laminated structure, which might be mistaken for 

 bedding planes. 



No. 1012. This was from an exposure near No. 1011, but separated from it by a 

 rivulet, and its connection with the other described masses could not be shown in the 

 field. This rock is much jointed, presenting an imperfect fissile structure, and is of a 

 dark green color, with yellow4sh-brown ochery spots of decomposition. On the weath- 

 ered surface, the magnetite shows the irregular sponge-like structure so characteristic 

 of all these rocks. The character of the section is like that of those last described, but 

 witli the addition to its alteration-products of considerable dolomite. I have no hesita- 

 tion in declaring my opinion, from the microscopic characters of this specimen, that this 

 outcrop belongs to the same formation as the hill itself. 



The specific gravity of the Cumberland palla.site varies according to the 

 state of the rock — whether altered or unaltered. Dr. Charles T. Jackson 

 states that it varies from 3.82 to 3.88. Mr. J. E. Wolff, Assistant in Coology 

 in Harvard College, kindly made some determinations for me. The specific 

 gravity of No. 998 was found to be 4.0G and 4.005. The former determina- 

 tion was made from a fragment containing almost no feldspar, while the 

 latter was made from one containing considerable. Again, a specific gravity 

 determination of No. 1001 gave as a result 3.5G, and of No. 1003, 3.55. 



The two latter determinations were made from the more higlily altered 

 portions of the rock. 



Owingc to the various alterations that this Cumberland rock shows, it 



