1 9<3 Arlijicial Incubation. 



temperature of the water falls, and its surface becomes 

 covered with ice. If the ball of a thermomtter be wrapped 

 in cotton, plunged in this liquid, and swung in the air, (when 

 the temperature of the room is ten degrees centigrade,) a 

 diminution of volume takes place, corresponding with the 

 temp' rature of fifty seven degrees centigrade, and if the 

 thermometer be placed in a receiver, and exhaustion pro- 

 duced, a degree of cold equal to sixty-eight degrees is easily 

 produced. Mercury may thus be frozen in the open air by 

 spontaneo'^is evaporation ; but more strikingly by putting a 

 little into a cup, adding to it a quantity of the liquid, and 

 exhausting the air from around it. Alcohol at thirty-three 

 dej^-rees, and below, has thus been frozen. 



This mode of cooling has been applied to the liquefaction 

 of otijer gases. The gas is first dried by parsing it tnrough 

 a tube con<aining muriate of lime ; to this tube is adapted a 

 tube beni at right angles ; the horizontal branch, swelling 

 into a thin ba«i whitb is surrounded with cotton, and mois- 

 tci-ed with 5u!phurous acid, ai'd the vertical branch plunging 

 into mercury, in this way the author has condensed chlo- 

 rine, ammou'a, and cyanogen. The latter has even been 

 obtained orystaliiz'd and solid. He now proposes to employ 

 this iast substance to the condensation of gases which resist 

 the former method. — Idem, Mai 1 824. 



35. Artifcial incubation. — An ingenious apparatus for this 

 purpose has been invented by Mr. Earlow, near London, in 

 which the requisite heat is maintained by the circulation of 

 steam. It consists of a box or oven constructed of iron 

 plates, divided into a great number of compartments, each 

 of which is warmed to the temperature requited. The eggs 

 are first placed in that which is the least heated, and are 

 gradually removed to that which is of the highest tempera- 

 ture. The more difficult part of the process consists in 

 regulating in a unifoim maniier the heat of each compart- 

 ment. The invt-ntor has accomplished this by placing 

 valves, fitted with thermometers, so as that they admit or 

 exclude the steam by the force of the heat itself It may 

 readily be conceived that, in an apparatus containing fifteen 

 hundred eggs, aqueous vapours would arise so copiously as 

 to mjure the success of the operation, had not means been 

 devised of absorbing them. A hydrometer of a particular 

 construction is destined for this purpose. 



