26 A. W. Wright—Production of Ozone with Hleciricity. 
the specular and earthy red hematites are nearly identical - 
and unlike any other iron ore I have seen. A sandstone associ- 
ated with the Missouri ores is very similar to the Pots- 
dam in lithological character, and the series is, I believe, 
regarded by the Missouri geologists as of Lower Silurian age. 
ron ores are described as occurring in the Potsdam period of 
Canada, but I do not know of any ore in the United States 
which the Geological Reports assign to that period. 
Art. VL—Ona simple Apparatus for the Production of Ozone 
with Electricity of high tension; by Prof. ArnrHur W. 
RIGHT. 
EXPERIMENT has shown that in the production of ozone by 
electricity the maximum amount of oxygen is ozonized by the 
silent or glow discharge, and most of the forms of apparatus by 
which this is effected are contrivances by which oxygen is made 
to flow slowly through a space traversed by such a discharge. 
n y. Babo’s apparatus, as well as in those of Siemens and 
Houzeau, the metallic conductors are separated by glass and a 
stratum of air. By inductive action of the charged metallic 
surfaces the intervening air becomes charged with electricity 
oppositely upon its two sides, and simultaneously with the 
discharge of the metallic terminals, through the wire of the 
coil, a discharge takes place through the air, not in the form 
of sparks, but diffusely, producing a glow of purplish light, 
visible only in the dark. 
_ These apparatus succeed best with electricity of compara- 
tively low tension. In using the Holtz’s electro-machine with 
them the discharge is apt to occur chiefly in the form of sparks 
through the air, or it may even traverse and perforate the glass, 
and the form of the apparatus must be varied to give the best 
results. 
_ When the poles of the machine itself are separated to a suffi- 
cient distance the electricity passes between ee either in the 
rm of a diffuse brush, spanning the whole interval, or with a 
very minute brush upon the negative pole, and a glow upon 
the positive, the intermediate space not being visibly luminous. 
is is the so-called dark or silent discharge, exhibiting the 
phenomena of the electric shadow when suitable objects are 
interposed, as described in a former paper.* When this occurs 
the strong odor shows that a considerable amount of the atmos- 
pheric oxygen is converted into ozone. 
* This Journal, II, xlix, p. 381, and III, i, p. 437. 
