G. Merry vveather*s Account <)fa new Apparatus. 361 



fluences ; and that it can be kept in constant operation, for an 

 indefinite period, without requiring any one to attend to it. 



It remains for scientific men to prove what its utility may be 

 in chemistry and in pharmacy ; and whether phenomena, at pre- 

 sent unknown, may not be produced by submitting different 

 substances, for a length of time, to the uniform temperature, 

 that this apparatus will maintain. Boerhaave first produced the 

 red oxide, by keeping mercury at the steadiest temperature he 

 could procure for many weeks. 



I rather anticipate an objection that may be made to this fur- 

 nace, ?. e» the expense of the spirit consumed : but every one 

 who has observed the constant attendance and watchings, which 

 every process requires where fire is employed, will easily per- 

 ceive, that what is expended in spirit will be more than econo- 

 mized in time. It will, I hop6, be sufficiently obvious, that, in 

 conducting experiments by this apparatus, there will be no fires 

 to mend, — no chimneys to sweep, (as it causes no smoke) ; and, 

 from the precision of temperature, there will be no danger of 

 explosions or boilings over. For instance, a practitioner may 

 commence his process of distillation in the morning, — he may 

 attend to the calls of his profession, and be satisfied during his 

 absence that all is going on steadily. — But, as the expense of all 

 processes is an important consideration, I have been induced to 

 make the following calculation : I find that one gallon of spirit, 

 twenty-two over-proof, which costs 9s. from the distiller, will 

 keep one of the balls incandescent for two months, night and 

 day ; or a fraction less than a penny for twelve hours. Three 

 burners cause a temperature of 160° of Fahrenheit ; — six pro- 

 duce a temperature of 215°; therefore, the expense of support- 

 ing the former for twelve hours will be 3d. and the latter 6d. 

 The apparatus, which is at present before the Royal So- 

 ciety, has fifteen burners elevating the temperature to near- 

 ly 396°, making the expense Is. 3d. for the same period. 



I am indebted to Dr Duncan, the Professor of Materia 

 Medica, for suggesting to me the amount of temperature I have 

 produced this evening before the Royal Society. And, I have 

 no doubt, if it had been necessary, I could have produced a 

 tenfperature of 1000° ; but I am informed, that a heat of 300° 

 to 350** is the most desirable temperature. 



It perhaps will be expected that I should give an analytical 



