Wadsworth. ] 288 [October 1, 
1st Variety. 2d Var. At. Ratio. 
H,O at 100° C. 36 36 
“ above 100° C, 11.26 11.22 1.24 
Si,O 44,22 44.22 2.95 
Fe,Os 6.61 a 25 
Al,O, 58 08 
MgO 87.54 87.40 1.88 
100.52 100.11 
Bases : Silica : Water Teg or dee 
2o16) 3) 20950 lod! 1.88 : .28 
2 Pee eta ape se (tft yt ae 
From this ratio is derived the following formula: 
f iv xii xii 
4(H-+8)3Si, or H,, Mz,0,,Si, 
The calculated percentages corresponding to this formula are as 
follows: 
DELO io ele (cb ga ciaba. | yey, ap ee eee rt 
BOBO Oe RE OST ae eri 
AMEOR jbl itl he ae » otip Logs ie tes Teen 
100.00 
On THE Iron ORE oF Barrtuett, N. H. By J. H. Huntine- 
TON, A.M. 
The mode of occurrence of the iron ore of Bartlett is so unusual 
that a detailed description of the rocks in the vicinity seems to be 
necessary. Beginning in the west part of Jackson, and farther south 
in the east part of Bartlett, extending thence across and up the val- 
ley of the Saco, there is a large area where granitic rocks prevail. 
The north line of this granitic area extends south-westward from a 
point a few rods north of Jackson Falls across the line of Bartlett, 
then along the south slope of the summit of Iron mountain. After 
crossing Rocky Branch it turns somewhat northerly, and crosses the 
mountain range between Rocky Branch and Mount Washington 
river just north of Giant’s Stairs. The southern boundary of this area 
is not so well marked, since in the vicinity of Mount Pequawket the 
granite is intimately associated with the porphyrite of that mountain. 
West and south of the Saco the granitic area extends far to the south- 
west, but the rocks we describe will be limited to the immediate val- 
ley of the Saco. . 
There are in this area three well-marked varieties of granite: 
