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436 



Scientific Intelligence. 



potassium is ihe most delicate. This is dependent upon an inexplica- 

 bllr but well known property of starch to be rendered blue by a very 

 minute portion of free iodine. A very small addition of chlorinej by 

 seizing an equivalent portion of potassium, liberates enough iodine to 

 produce blueness in mixture; and, in like manner, a \e)'y small pro- 

 portion of ozonized air, whatever may be its source, renders starch 



blue by a like procedure, ■ - 



■In like manner, by exposure to ozonified air, strips of paper, drench- 

 ed with a tincture of gum guaiacum, are rendered blue, as these changes 

 would have resulted from the presence of chlorine, and as neither that 

 nortJny other of the known halogen bodies could be present, the agen- 

 cy of some undetected body of that class was reasonably to be inferred. 



Having given this preliminary brief sketch of the state of our knowl- 

 edge respecting ozone, it is time to proceed to explain its connectioa 

 with the contrivance of the apparatus before us. 



■ It had occurred to me that the smell and corruscations arising from 

 the attrition of siliceous stones, briskly rubbed against each other, might 

 be due to some cause, analogous, if not identical, with that to which 

 the phenomena of ozone are indebted for their existence. 



Nothing could be more unaccountable than this odor. That it can- 

 not be due to any organic matter entering into the composition oi the 

 quartz must be evident ; in the first place, because the smell is produced 

 by the purest and most transparent specimens of rock crystal in the 

 regular form, and in the second place, because ignition to bright red- 

 3 does not destroy nor even diminish the property. 



One thousand grains of cellular horn stone, or French burr, on igni- 



tion 



above stated, lost five grains 



that is to say, one-half per cent 



- - ' light 



of its weight, without, however, losing the property of producing 

 and smell. 



It occurred to me that It might help to remove the mystery, were aa 

 apparatus constructed by which the attrition of siliceous masses might 

 be made more efficaciously than could be effected by an operator un- 

 aided by mechanism. Having suggested this idea to my friend, Prof. 

 Henry, he said that I might have such an apparatus constructed at the 

 expense of the Smithsonian Institution. The apparatus, which is be- 

 fore the meeting, was made accordingly. 



Two pigmy mill-stones, each seven inches in diameter, made of cel- 

 lular horn stone, known vulgarly as French burr, and resembling those 

 used in grist mills, were procured and supported as in the usual way, 

 one above the other ; excepting that the upper one hangs by means of 

 a bolt upon a spiral spring of brass wire, sustained by a cross of iron, 

 resting upon screw nuts, upheld by four iron rods, each inserted at its 

 lower end in a circular plate of cast iron, so as to be equidistant from 

 each other. The surface of the iron plate is turned true, so as to ena- 

 ble it to serve as an air-pump plate. It rests upon four columns, which 

 elevate it from a base board sufficiently to admit of a pulley band and 

 wheel to work in a parallel plane below that in which the plate is situ- 

 ated. There is also room for a lever, from which a stirrup hangs as a 

 support for ihe spindle of the pulley, on the apex of which plane ex- 

 tended upwards through a perforation in the axis of the plate, the low- 

 er mill-stone rests. This spindle passes through a stuffing box, so as 



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