3i Experiments upon the 



cordingly *, exhaust the globe F, and proceed with the ex- 

 periment as described bv M. Van Marum. 



An operation may be continued any length of time with- 

 this gasometer, without altering the pressure, by filling D 

 and E with the requisite gas during the experiment, which 

 is performed tlius : the gas-holder V being charged, screw 

 the cocks v and z on to u and x, and the water will run into 

 V until the gas is exactly of the same density as that in D 

 or E : shut tc and i', arid' screw on to / ;. open t, v, x, and z y 

 and the gas in V will be transferred into E, without alkring. 

 the efl'ecti've pressure, P?oeeed in> the same mannsr with the 

 gas intended for D. 



V. Experiments vpon the various Species of Cinchona. By 



M. VAUaUELIN t. 



! 



§ I. 



Vhjsical Properties of Cinchona, 



Xn eomm«rGc, many different species of cinchona are known j 

 the principal and most frequently employed species, however, 

 are the following : 



The first, antiently known by the vague name of Peruviaih 

 bark, appears to be that produced from the tree called by 

 Linnaeus cinchona officinalis. This species has a grayish 

 colour externally, and a pale red internally ; it is very thin, 

 rolled inwards on the side which adhered to the wood ; hav- 

 ing a glossy and as it were a resinous fracture, sometimes 

 slightly fibrous ; an astringent and bitter taste. It yields 3 

 fawn-coloured powder mixed with gray. 



* Tlie eficcthrc piessure will always be as the hefght of the orifice H above 

 that of tlic recurved tube y; and this pressure will continue uniform and pre- 

 cisely equal in both vessels, without regard to the quantity of v/ater in A. 



For the mode of fillinj,' A during an experiment, as well as for further par- 

 ticulars relative to the principles of this instrument, see description of the 

 Hydrostatic Regulator, Phil. Mag. vol. XX. p. 289. — J. S. 



Sec ifso' Mr. Stce\'ens'» description of his Single Gasometer, vol. :^xi v.,p. 1 C.IJ. 

 — EniT. 



S from Avi2lcs dc Chvnlc, torn. lix. p. II:,'. 



The 



