334 History of Mechanical Inventions, and 



out the province of Nemaur, but in greatest abundance along the foot of 

 the Vindhya range of hills in the vicinity of Jaum Ghat, and thirty miles 

 further west on the table land of the same range, near Nalcha, at which 

 two places only I believe it is prepared, at least to any amount. About 

 the latter end of August, it begins to bud, and continues to flower in 

 tolerable vigour till the end of October, during which period alone it gives 

 out the oil in sufficient quantity to cover the expence and trouble of its 

 preparation, as after this it speedily dries up, and what little oil it does 

 yield is extremely acrid, and unfit for use. 



The oil is obtained from the grass by distillation, by means of an ap- 

 paratus simple enough in its construction, some little improvement on 

 which, it is probable, might give it more power. A wrought iron boiler 

 is fitted over an earthen fireplace, and surmounted with a capital, from 

 which two straight tubes, from five to six feet in. length, and two inches 

 in diameter, conduct the vapour into a couple of large copper receivers, 

 immersed in cold water. At the conclusion of the process, the condensed 

 fluid is poured into a large wide-mouthed vessel, and permitted to stand 

 for some time, when the oil may be skimmed off the surface with a small 

 shallow spoon. The plant is cut across where it begins to give out its 

 flower, and bound up into small bundles or maniples, 250 or 300 of which 

 are placed in the boiler, and so much water poured over them as to leave 

 a sufficient space for ebullition, which is immediately promoted, without 

 any previous maceration. The process occupies about six hours ; and as 

 there is a succession of attendants, it suffers little interruption, being usu- 

 ally accomplished four times in twenty-four hours, in which time about 

 one seer of the oil is obtained. It is volatile, and extremely pungent, of a 

 very light straw colour, and beautifully transparent, giving out a pecu- 

 liarly rich and grateful odour, which diffuses itself very widely, if the ves- 

 sel containing it is left unstopped. The price set upon it by the distiller 

 is altogether disproportionate to the actual expence incurred in its prepa- 

 ration, as on calculating the cost of labour and materials, at rates even ad- 

 mitted by the Jaum manufacturer, I conceive that an average price of £ per 

 quart would cover all his expences, and allow him an equitable recom- 

 pense for his trouble. But there is no hope of being able to effect so con- 

 siderable a reduction, while he can realize so much more by disposing of 

 it elsewhere. 



4. Theory of Sir H. Davy's Safety Lamp. By G. Librl 

 An interesting paper on the nature and properties of flame was read by 

 G« Libri, at the Society of Georgofili (Florence) on the 3d of Decerriber 

 1826. The author was led to doubt the correctness of the theory or expla- 

 nation given by Sir H. Davy, in order to account for the phenomenon of 

 his safety lamp. The distinguished inventor ascribes the security which 

 the lamp affords to the conducting power of the metallic gauze, by which 

 it is supposed the temperature of the flame is so much lowered as to be in- 

 sufficient to ignite the inflammable mixture on the outside. Some facts 

 known to the author were at variance with this hypothesis ; and he found 



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