344 Anali/sis of Hcicnt^c Books. 



" Steam is uow used extensively for drying muslin and calicoes. Large 

 cylinders are filled with it, which, diffusing in the apartment a temneratnre 

 of 100° or 130°, rapidly dry the suspended cloth. Occasionally the clotW 

 is made to glide in a serpentine manner closely round a series of steam cy- 

 linders, arranged in parallel rows. It is thus safely and thoroughly dried 

 in the course of a minute. Experience has shewn, that bright-dyed yarns 

 like scarlet, dried in a common stuve heat of 128°, have their colour dark- 

 ened, and acquire a harsh feel ; while similar hanks, laid on a «<fani-pipe 

 heated up to 165°, retain the shade and lustre they possessed in the wetted 

 state. The people who work in steam drying-rooms are healthy ; those 

 who were formerly employed in the stove-heated apartments, became soon 

 sickly and emaciated. These injurious effects must be ascribed to the 

 action of cast iron, at a high temperature, on the atmosphere." 



The true theory of the formation of coal-gas is clearly 



stated in the following short paragraph. 



" If coal be put into a cold retort, and slowly exposed to heat, its bitu- 

 men is merely volatilized in the state of condensible tar. Little gas, and 

 that of inferior illuminating power, is produced. This distillatory tem- 

 perature may be estimated at about (J00° or 700° F. If tlie retort be pre- 

 viously brought to a bright cherry-red heat, then the coals, the instant 

 after their introduction, yield a copious supply of good gas, and a mode- 

 rate quantity of tarry and amnioniacal vapour. But when the retort is 

 heated to nearly a white incandescence, the part of the gas richest in 

 light, is attenuated into one of inferior quality, as I have shewn in detail- 

 ing Berthollet's experiments on Caeburetted Hydrogen. A pound of 

 good cannel coal, properly treated in a small apparatus, will yield five 

 cubic feet of gas, equivalent in illuminating power to a mould candle six 

 in the pound. See Candle." 



We meet with a number of useful rules for conducting che- 

 mical computations, in different parts of the dictionary. The 

 reader will find several curious ones in the last article, as well 

 as under Gas. The article Comhustion may be regarded as 

 presenting Dr. lire's ideas of chemical theory. We shall 

 quote one or two passages from it. 



" Combustion. The disengagement of heat and light which accompanies 

 chemical combination. It is frequently made to be synonymous with in- 

 flammation, a term which might be restricted, however, to that peculiar 

 species of combustion in which gaseous matter is burned. Ignition is the 

 incandescence of a body, produced by extrinsic means, without change of 

 its chemical constitution. 



" Beccher and Stahl, feeling daily the necessity of fire to human ex- 

 istence, and astonished with the metamcn-phoscs which this power seemed to 

 cause charcoal, sulphur, and metals to imdergo, came to regard combustion 

 as the single phenomenon of chemistry. Under this impression, Stahl 

 framed his chemical system, the Theorin ChemicB Dogmatica, a title charac- 

 teristic of the dogmatic spirit with which it was inculcated by chemical 

 professors, as the infallible code of their science for almost a century. 

 When the discoveries of Scheele, Cavendish, and Priestley, had fully de- 

 monstrated the essential part which air played, in many instances of com- 

 bustion, the French school made a small modification ot the German hypo- 

 thesis. Instead of supposing, with Stahl, that the heat and light were 

 occasioned by the emission of a. common inflammable principle from the com- 

 bustible itself, Lavoisier and his associates dexterously availed themselves 

 of Black's hypothesis of latent heat, and maintained, that the heat and 

 light emanated from the oxygenous air, at the moment of its union or fixa- 

 tion with the inflammable basis. How thoroughly the chemical mind has 

 been perverted by these conjectural notions, all our existing systems of 

 chemistry, with one exception, abundantly prove. 



" Dr. Robison, in his preface to Black's lectures, after tracing, with per- 

 haps superfluous zeal, the expanded ideas of Lavoisier to the neglected 

 jjerms of Hooke and Mayhow, says, ' This doctrine concerning combustion, 

 the great, the characteristic phenomenon of chemical nature, has at last 



