74 On the ufe of Chrome, 
B is acircular milled proje€tion on one end of the lever 
BK, and ferves as a thumb-piece to be prefled imto the 
fhank againft a {pring placed below the fame end of the 
lever; by which means the end K is raifed fo as to unlock 
the claw when it is withed to be turned to another fide of the 
inftrument. 
H thews a feGtion of this part of the inftrument, where I 
reprefents the {pring that is acted upon by prefling down the 
ihumb-piece B, fo as to raife the end K of the lever, to dif, 
charge it from the notch in the heel of the claw when the 
latter is wifhed to be moved to a new pofition. 
C, the claw, is made to come off flat at its lower extre- 
mity, and roughed on the infide, which, with the fhoulder ° 
E, forms a bed to receive the tooth, 
D, the bolfter, is made concave, to anfwer to the con- 
‘ yexity of the teeth. 
G, the heel of the claw, has four, fix, or a greater num~ 
ber of notches round it, fitted to receive the end K of the, 
Jever. 
The improvements introduced into this inftrument are 
fuch as I hope will be found to remedy the defeéts com- 
plained of in all former ones; and the facility with which a 
tooth can be drawn by its means, will, I am fure, render 
its adoption in practice univerfal gts foon as it fhall be ge- 
nerally known. iz , 
A 
XV. On the Ufe of the new Metal called Chrome, tbe Oxyd 
of Chrome, and the Chromic Acid, By Cit. VaUQUELIN, 
From the Journal des Mines, No. XXXIV. 
Tue fragility of chrome, the refiftance it offers to the 
action of fire, and the fmallnefs of the maffes in which tt 
has hitherto been naturally found, do not leave us any hopes 
that this metal can ever be of great utility in the arts. This 
affertion, however, may be going rather a little too far; for 
a new fubftance, the propertics of which do net at firfi feens 
hkely 
