Genth.] 694. (Oct. 17, 
The position of this belt is indicated, ©, (l. ci.), as follows: * * * 
“These slates are bordered by a great belt of serpentine, of which 
the northern boundary is nearly parallel with the southern margin of the 
limestone itself, as if the mass of schists intervening had about a uniform 
thickness, and that the serpentine were a true contact formation occurring 
between these schists and the lower rocks.” 
Attention was drawn to another statement of Prof. Lewis, viz: that the 
lithological characteristics of this dyke were constant throughout its range. 
This was entirely at variance with the speaker’s observation. There were 
strongly marked differences of texture, structure, and constitution between 
many of these outcrops in the townships south of the Chester valley, and 
near Conshohocken. 
On Herderiie. By F. A. Genth. 
(Read before the American Philosophical Society, October 17, 1884.) 
In the American Journal of Science [8], xxvii, 185-188, in an article on 
Herderite, by William Earl Hidden and James B. Mackintosh, the latter 
published his analysis of this rare mineral from Stoneham, Me. In aletter 
{o the editors of the ‘Neue Jahrbuch der Mineralogie, &c.,’’ of 1884, ii, 
134-136, Professor A. Weisbach gives the results of a comparative exami- 
nation of the original herderite from Ehrenfriedersdorf, Saxony, and of 
that of Stoneham, Me., made at his suggestion by Dr. Cl. Winkler. 
These investigations, showing remarkable discrepancies not only be- 
tween Dr. Winkler’s analyses of the herderite from the two localities, but 
also between those of the two analysts of the Stoneham mineral, it was 
desirable to re-examine this interesting species. 
Tam under great obligations to Mr. George F. Kunz, who has kindly 
furnished me with the material for this investigation, from which I was 
able to pick out over 2.5 grms. of pure crystals, 
Referring to the occurrence of herderite, he has sent me the following 
communication, dated New York, October 14th, 1884 : 
“On revisiting the Stoneham locality I found that the herderite had all been 
‘obtained from a vein of margarodite, four feet wide, about twenty feet long, 
“worked to a depth of ten feet. This vein is on the side of the top of Harndon 
“hill, about one hundred feet from the place where was found the topaz obtained 
“py me (see Proceedings New York Academy of Scieuce, November and De- 
“cember, 1842, and American Journal of Science, Feb,, 1883), and not in the same 
“pocket, as stated in the article, in the American Journal of Science, Jan. 7, 
«1884. The vein is almost entirely margarodite, occurring here in unexampled 
“crystals. These at times cover spaces four or five inches square with distinet 
“perfect crystals of margarodite, also altering to serpentine, and associated 
“with it what is possibly topaz, altered into serpentine, 
“The herderite occurs almost invariably in erystals, implanted on the mar- 
“ varodite, crystals of quartz, and in a few instances on columbite, 
“ Between the herderite vein and the topaz vein worked by me were found the 
“large columbite and triplite, Two distinet crystals of triplite have been found 
“recently. 
“Signed, GHORGE F, KUNZ.” 
