

. 



F 



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ii 



Chemistnj and Physics. 437 



I 



to be air-tight ; the stirrup allowing it to retain its perpendicularify, not- 

 withstanding the curvilinear movement of the lever when employed^lo 

 raise or lower the stone. 



The nuts upon which the cross supporting the upper stone has been 

 mentioned as resting, are so used as to render the lower surface of the 

 stone horizontal, while, as h hangs upon a bolt which occupies the axis 

 of ihe spiral spring, the pressure on the lower stone, when brought 

 into contact with it, may be made as gentle as necessary. The lower 

 stone being balanced on the point o^ ihe spindle, is made lo turn with 

 It by means of a pin proceeding from its lower surface and another 

 proceeding from the spindle, which operates as a carrier in a lath^. 



In order to put the apparatus in operation, the lower stone is niade to 

 revolve by means of the pulley, band, andvvheel; wfiile, by means of 

 the lever, the stone is so raised as to produce sufficient contact with 

 that suspended above it. Under these circumslances, scintillation and 

 the odor which is the object of inquiry resulted. In no way, however, 

 could I produce the chemical effects of ozone upon iddized starch or 

 guaiacum. On directing a jet of hydrogen between the stones, it took 

 fire forthwith ; but 1 could not, by means of an electrometer, detect any 

 electricity. When the upper stone was removed, and a piece oi an . 

 old file of a large size made to scrape over the surface of the lower 

 stone, a conducting connexion between the file and an electrometer 

 was productive of no electrical indication. 



The plate being ground to fit a large receiver, the stones were in 

 successive experiments made to revolve in vacuo, in hydrogen, and in 

 a vacuity previously replete with this gas, wiihout any diminution of 

 the luminous phenomena. These, it seems from the inflammation of 

 the jet of hydrogen, constitute a simple case of ignition. During the 

 collision of flint with steel, a portion of the metal being struck off, takes 

 fire, and thus is enabled lo convey ignition to tinder or punk. The in- 

 capacity of two pieces of quartz to produce fire in like manner, arises 

 from the incombustibility of the particles struck off from them, which 

 consequently cool before they meet any mass with which they are not 

 in contact at the moment when the ignition supervenes. 



As the burr stones are opaque, the light is much less advantageous- 

 ly seen when they are both employed, than when the upper one is re- 

 placed by a comparatively small mass of transparent quartz. The 

 concentration of the frictional force, and the transparency of tlie mass 

 under which the ignition is effected, makes the corruscations very brtl- 

 hant in a room otherwise darkened. 



So great is the resistance of the surfaces of the stones when brought 

 into revolutionary collision, that the maximum effect which they are 

 capable of producing, would require more force than can be communis 

 cated by the human power, through a single hand actuating the stones 

 by means of a wheel, pulley, and band. 



Of course cog wheels might be resorted to, and the power of steam 

 or that of Professor Page's electro-magnetic machine, employed to ob- 

 tain a greater effect. I have lately been informed, that in English pot- 

 teries where flint is employed as an ingredient in the ware manufactur- 

 ed, the grinding of this material is productive of an intolerable foetidity* 

 In an atmosphere thus imbued with foetidity, chemical effects ought to 



Second Skeies, Yol. XII. No. 36.— XoT^ 1851. 66 



