25o ObfcwailoHS on MatlJering^ 



on longitudinal vibrations. There is this diflerencc, however, 

 that, as far as I have oljfcrved, the tone, uhen tiie wbrations 

 take place in a fpiral direction, is a fifth lower than wlien the 

 rod vibrates in a longitudinal direttion under the fame cir- 

 cumfiances. 

 ■ By the fpiral vibration one phaenomcnon, which I have 

 mentioned in niy difcoverics rcfpefting the theory of found, 

 but refpefting which I formed an erroneous opinion, can bff 

 explained. On a prifmatic rod, one end of which was faftened 

 in a vice, when I rubbed one of its edges, in a diagonal di- 

 reftion, with a violin bow, and ftrewed fand over one of its 

 horizontal fides, there appeared on this fide a line proceeding 

 along its length, where the fand, whicl\ was thrown from the 

 other parts by the vibration, remained at reft; and this ap-^ 

 pearance took place on each fide of the rod when held hori- 

 zontally. The reafon of this is, becaufe at the edges which, 

 are further diftant from the axis the range during the vibra- 

 tions is greater than in the middle of each fide; and on this 

 account the fand which is thrown from the nearer places to 

 thofe on the edges mufi accunuilate themfelves longitudinally 

 in the middle of each fide neareft the axis where the vibra- 

 tions are weakelt. 



Xl-'^TI. Ohfer'i'athns on jSInddrring', Ingclher iinth a Jimple.. 

 /ind ciTlain Procej's Jar ohtaimrig, Kvith great Brautv and. 

 Fixity, that Coioiir knotuji midcr the Name of the Turkej or 

 Adrianoplc Red. Bj J. IVl. H A u s s M A N N . 



[Concluded from p. 175.] 



. The Frocefs, 



_/ jlFTER making a cauftic ley of one part of sjood common 

 potafh difl'olved in four parts ofboilino; water, and half a part 

 of quicklime, which I afterwards fiaked in it, I dilfolved one 

 part of powdered alum in two parts of boiling water ; and while 

 this folution of fulphatc of alumine was ftill warm, to avoid 

 re-cryftallization, I fpeedilv poured into it fucceffivcly, always 

 ftirrins; it without interruption, the above-mentioned cauftic 

 ley, till the alumine it had at firft precipitated after laturation 

 to excefs with fulphuric acid had been redifl'olvcd. I left at 

 reft this folution of alumine, which exhaled anmionia, and 

 which, on cooling, formed a precipitate of fulphaie of potafh 

 in very fmall cryftaLs. I then mixed a thirty-third part of 



Jinfeed- 



