46 Vfeful Nottcet. 



and the nitrate of lead, are not dccompofed, but the acetite of lead is Immediately decom- 

 pofed and precipitated in a white powder. The nitrate and acetite of mercury are alfo dc- 

 compofed, and the mercurial citrate which falls down is a flaky fait, of a brick-duft co- 

 lour, more or lefs red. The citric acid gives a green tinge to the folution of the acetite and 

 fulphate of iron. 



The quantity of citric acid which I obtained being conGderable, I intend hereafter to 

 give an account of the phenomena it exhibits in its different combinations. 



XIV. 



Ufeful Notices refpeHing various ObjeHs. — Governor for regulating the Motions of Steam' 



Engines. — Amelioration of Oil. 



T. 



Governor for regulating the Motions ofSteam-Engines. 



H E apparatus mentioned page 424 of the prefcnt work by the name of a Governor, is 

 there fuppofed to be the invention of Mr. "Watt. My fuppofition was grounded upon no 



other fa<5t than that of having feen it in his engines. It was invented by Bunce, Efq. 



of the Admiralty, who applied it to a crane feveral years ago, the conftru£lion of which 

 was communicated to the Society of Arts, foon after which period it was adopted in fteam- 

 engines. I cannot now refer to the volume, as I do not pofTefs the fet. But I had the in- 

 formation from the inventor himfelf. 



■2. Amelioration of Oil. 



EVERY one who has occafion to ufe lamps muft be fcnfible that the colour of the lights 

 as well as the quantity and kind of difagrceable vapour emitted from the flame, depends 

 greatly on the quality of the oil. When oil is kept in an open veflel, it gradually becomes 

 more and more oxygenated, and at the fame time lefs fluid. For both thefe reafons it is 

 lefs fit for ufe. It is lefs combuftible, and lefs adapted to pafs between the fibres of the 

 wick. Thefe obfervations point out the expediency of keeping oil in well-clofed veflels. 

 The fluidity of whale-oil, and the facility of its combuftion, may be confiderably augmented 

 by an addition of cold-drawn linfeed oil. 



It is well known that oil may be rendered purer by agitation with water, more particu- 

 larly with the addition of an acid. The.effeft of this procefs is dated to be, that it carries 

 off a portion of mucilage, which is not adapted to anfwer the purpofes to which oil is applied. 

 It may eafily be imagined, however, that oil thus treated will retain a portion of aqueous or fa- 

 line matter, which may render it unfit to be applied to the moving parts of inftruments for 

 the purpofe of diminilhing fridlion. Some clock and watch makers expofe olive-oil to the 

 atmofphere in frofty weather ; and feleft that portion which they find to continue fluid 

 after a confiderable part is frozen. This proceeding is grounded on the fuppofition, that 

 the oil may confift of two different fluids, one of which is fuppofed to congeal in a lefs heat 

 than the other ; and that this congelation is the principal evil which happens to the oil ia 

 iime-pleces. It does not feem probable that either of thefe fuppofitions arc well feanded. 



FfiT 



