350 History of' Mechanical Inventions, tyc. 



M. Dobereiner of Jena conceives that the phenomenon now described is 

 the effect of an electro-magnetic action ; and he proposes to try if the 

 brass wire would not sound when it communicates at its extremity with 

 an energetic electrometer. Bullet, des Sc. Techn. &c. July 1824, p. 51. 



12. Natural Lamp by Incandescence. 



In using a spirit of wine lamp, M. Dobereiner observed, that when the 

 spirit of wine was nearly consumed, the wick became carbonised, and 

 that the flame disappeared, yet the carbonised part of the wick became 

 incandescent, and continued red while a drop of alcohol remained, pro- 

 vided the air in the apartment was tranquil. In one experiment it con- 

 tinued red twenty-four hours ; a disagreable acid vapour, however, was 



formed. 



Dr Brewster long ago observed an analogous fact in the small green 

 wax tapers in common use. When the flame is blown out, the wick will 

 continue red for many hours, and the wax and wick are burned down as in 

 its ordinary combustion, only with extreme slowness ; a very disagreeable 

 vapour being formed during the imperfect combustion. Dr Brewster has 

 observed also, that the same effect is not produced when the taper is made 

 of red wax. This probably arises from the colouring matter of the two 

 tapers. There can be little doubt, however, that the same result will be 

 obtained with different kinds of wax, and even with tallow, provided the 

 quantity of wax is properly proportioned to the diameter of the wick. 



13. Oil for Chronometers, Clocks, and Delicate Wheel-work. 



It has long been a desideratum among watchmakers to procure good oil, 

 that retained its fluidity for a length of time, without acting upon the 

 metals which it lubricated, and without becoming thick or freezing with 

 Cold. For this purpose, every kind of acid, or of mucilage, must be taken 

 from it. In short, it should be pure elaine, without any trace of stearine. 



In order to extract the elaine from fixed oils, M. Chevreul treats it in a 

 matrass, with seven or eight times its weight of alcohol nearly boiling, 

 decanting the liquid, and exposing it to the cold. The stearine will then 

 separate in the form of a crystallized precipitate. The alcoholic solution 

 must then be evaporated to the fifth of its volume, and the remainder 

 will be elaine, which ought to be colourless, insipid, almost without 

 smell, without any action on the infusion of turnsole, having the con- 

 sistence of white olive oil, and coagulable with difficulty. M. Peclet's 

 method of procuring elaine, consists in pouring upon oil a concentrated 

 solution of caustic soda, stirring the mixture, heating it slightly to sepa- 

 rate the elaine from the soap of the stearine, pouring it on a cloth, and 

 then separating by decantation the elaine from the excess of alcaline solu- 

 tion. Some excellent observations on the effects of oil in jewelled holes, 

 &c, will be found in the Edinburgh Encyclopaedia, Art. Horology, vol. 

 xi. p. 13T. 



