14 J.D. Whitney on Minerals of the Lake Superior region. 
the same large specimen, one object being to ascertain what the 
variations in the geen of oxygen were, in different portions 
the same mass. is the mean of three losely- agreeing de- 
pera oo 
the above analyses, the iron having been precipitated from 
the saileundigrisie acid solution by ammonia, the filtrate was 
evaporated to dryness and ignited, and in no case did the re- 
siduum amount to more than a few hundredths of one per cent. 
In I.c, and 111.5. there was a weighable quantity of lime present, 
amounting, in each case, to 0°05 per cent. It was not possible, 
in any instance, to obtain a ia ——— of alumina. The 
oxygen was therefore determined by the loss, as giving - 
accurate results than could be obtained by the process of re 
tion with hydrogen. It appears, therefore, that these ores re 
— 
mixtures of the peroxyd with a minute and varying portion of | 
the magnetic oxyd. 
Both the Burt and Cleveland Mountain ores show minute 
ple = of = acpi scattered through their mass; in the Burt 
re these are from ;'; to ;; of an inch in diameter ; in 
he Cleveland, so small as to q, hardly visible without a magni- 
ape glass. No sulphur or arsenic could be detected in any of 
imens examined. ‘The insoluble portion consists of sili- 
% vith only traces of lime, alumina and magnesia: this silica 
is partly in combination with the iron in the form of a silicate 
of iron, and partly present in the form of grains of quartz. 
the whole, it may be said with truth that these ores surpass in 
ity any known to exist elsewhere in the world in anything 
e the same quantity. 
Leonhardite.—This mineral has been observed only in the Old 
Copper Falls vein, where it was very abundant; but a care careful 
ee ee. would probably reveal its presence at other locali- 
n examination was made of this mineral to ascertain at 
what temperature it parts with a part or all of its water, with 
reference to H. Rose’s investigations on Laumontite, which he 
has shown to lose a portion of this Spnetiinent. at 100° C. The 
results gave on the mineral in small fragments 
Dried at Loss of weight: 
-.: - + 1-46 per cent. 
90° = 6. 3 
BOS cm « : o.|hU 
Ignition, - + - 1189 « 
The 1-46 per cent is probably ne essential to the constitution 
-of the mineral; the loss by ignition agrees well with the for- 
ign 
pene which takes the oxygen me of the bases and silica as 
| .: 
Lamonite..'This ore of iron has recently been discovered and 
for the first ‘time on Lake Superior in any Diciaciai sai 
