226 T. S. Hunt on Ophiolites. 
a large amount of magnesia with disengagement of carbonic 
acid; the solution contained besides, magnesia, iron, manganese, 
and a trace of nickel, but no lime. The undissolved residue 
was then boiled with a solution of carbonate of soda, which 
took up a considerable amount of silica derived from the silicate 
which had been partially decomposed by the nitric acid, and le 
a dense granular matter, mingled with silvery scales of greenish 
tale, which were in great part removed by washing. The 
denser silicate was then dried at 250° F., and submitted to analy- 
sis. By ignition it lost 11-40 per cent, and then gave toa boiling 
solution of nitrate of ammonia a quantity of magnesia equal to 
1:21 of carbonate. Another portion was decomposed by sul- 
phuric acid, and the silica separated from the insoluble tale by 4 
solution of carbonate of soda. The results of the analysis were 
as follows :— 
Silica, : : ‘ : : ‘ Y Wee 
* = 2 . - - 36°72 
Protoxyd of iron, - - - . “ - 486 
Oxyd of nickel, - : a - {traces.) 
ale, - - - - “ . = - 6°80 
Water, - - : 3 ™ “ > 10°77 
Carbonic acid, ; . . ; é nen 
99°38 
Deducting the talc, the carbonic acid, and the amount of mag 
nesia required to form with it 1-21 of carbonate, we have for the 
composition of this silicate dried at'250° FE. :— 
Silica, - . - ' P > - 43°34 
Magnesia, baad > - al - - 89°55 
Protoxyd of iron,  - - . * . «| 682 
Oxyd of nickel, - : . . “ (traces.) 
Water, - - - " s w - ANd 
100-00 
This is the composition of serpentine, and the ophiolite of 
Roxbury is thus shown to consist of serpentine and tale, inter 
mixed with a ferriferous carbonate of magnesia; the compa 
asbestus of Dr. Hayes is nothing more than serpentine. 
In the second part of this paper I propose to describe among 
ers, some of the ophiolites of the Faarensian series. 
ile 
