Thermomitr'ical FirJI-movers. Dying, 17S 



5t raiK^otn : I fliall therefore only remark, that the power of this wheel is very confiderable, 

 und may be encreafed aimoft at pleafure, by enlarging the dimenfious of the bars, in the 

 dirt£lIon parallel to the axis of the cylinder. 



Whatever queftion there may be, with regard to the force and durability of this fyftem of 

 bars, neither of which I am difpofed to doubt, there can be fcarcely any with regard to the 

 fpiral chain round the cylinder. The direft expanfion and contraction of metals is certainly 

 very powerful, and was (hev/n in a ftriking manner by the Rev. Mr. Jones in an experiment 

 related, if my memory be correal, in George Adams's Philofophical Ledtures. He hung a 

 very heavy weight to the longer end of a lever, the fliorter arm of which prefled upwards 

 againft the longer arm of another lever, and the fhorter arm of this laft was fupported by a 

 rod of metal. By this mechanical arrangement, it will be underftood, without difficulty, that 

 a very flight motion of the arm which bore upon th& metal, might be attended with a very 

 confiderable motion of that extremity which fupported the weight ; and the dimenfions were 

 fiich, that this was in fa6t the cafe. I'he flame of a candle applied to the bar of metal caufed 

 it to expand, and carried up the load without difficulty. 



Hygrometric contradlions and dilatations are known to be performed with immenfc force; 

 but want of durability in the materials, and the difficulty with regard to expofure, which has 

 been already mentioned, feem to forbid the praiSical ufe of this power for the purpofes to 

 which our attention is now dire£ted. 



The contrivance, fig. 5, may be confidered as effeiElual ; but the objections which have been 

 made to Ellicott's pendulum, are ftill more flrongly applicable to this, namely, that the 

 fridtion, the wear, and the irregular adlion of the joints, muft be hurtful to the general efFeft. 



VII. 



EJfcys on the Art of Dying, by Means of the Solutions of Tin, and the coloured Oxides of that 



Metal. By J. M. Haussman*- 



1 HIS memoir of Citizen Hauflman contains the refults of his numerous experiments on 

 the folutions of tin, and the oxydes of that metal ; refults which, as well as the obfervationS 

 of the author, are very interefting, not only with regard to the improvement of the art of 

 dying, but likewife with regard to our fcientific knowledge of the different degrees of the 

 oxygenation of metals, the union of their oxydes with their folvents, and the furcompofitions of 

 which thofe oxydes are fufceptible. 



The author commences his paper by announcing, that fmce the time of his refearches con- 

 cerning the Turkey red, of which a defcription is inferted in the twelfth volume of the An- 

 rales de Chimie, he has difcovered a red which is no lefs fimpie than beautiful and folid, the 

 procefs of which he intends fpeedily to publifli. 



* Abftraft from the memoir of the author bearing the fame title, by C. A. Prieur, in the Annales de 

 Chimie, XXX, 15, of which the prefent article is a tranflation. 



A a 2 He 



