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the two receivers neareft the retort were chargedwith four ounces of chalk diffufed in diftilledwater, while the third receiver contained afolution of cauftic potafh. In the fecond fetthe two firft receivers contained diftilled water,and the laft was charged with the wafhed chalk.In the third fet the two firft receivers containedlimewatcr; and in the fourth fet a folution of•cauftic potafh, the third receiver in both cafesholding the chalk. They were all equally expofedto the fame temperature, namely, from 74 0 to8o° Falir. for fix months, and the changes whichtheir contents had undergone were then exa-mined.

The chalk in the firft apparatus afforded a 6grs. of nitrat of lime mixed with a little nitratof ammonia; the potafh in the third receiverhad become faturated with carbonic acid andhad partly cryftallized on the fide of the receiver,but contained no nitre.

In the fecond apparatus the water of the twofirft receivers had acquired a very putrid fmellfrom the gas which had paffed through it, andcontained a little ammonia but afforded nonitrous fait on evaporation: the chalk in thethird receiver afforded by lixiviation no morethan 4 grains of nitrated lime.

In the third apparatus the lime water haddepofited its earth in the ftate of carbonat, andthe fupernatant fluid had a ftrong odour refem-bling ammonia and putrid garlic: by evaporationIt yielded 5 or 6 grains of nitrated ammonia.The chalk in the third receiver gave only aflight trace of nitrat of lime.

In the fourth apparatus the potafh was cryf-tallized but contained no nitre: with fulphuricacid it effervefced ftrongly, giving out a verypungent and highly fetid gas: the chalk in thethird receiver gave no indications whatever ofdie prefence of any nitrous fait.

The gas remaining in the receivers and col-lected in the pneumatic apparatus was in allthe four experiments found to be flightly in-flammable, although when rifing from theputrefying materials it extinguifhed a taperammerfed in it. This putrid inflammable gaswas incapable by itfelf of nitrifying chalk, butwhen mixed with wafhed atmofpheric air, car-bonic acid foon made its appearance, and thenthe gas became capable of impregnating chalknitrous acid as at firft.

The above experiments were undertakenWhen pneumatic chemiftry had as yet made butlittle progrefs, and therefore the deductionstrom them are by no means equivalent to the

labour and time employed in carrying diem on:it appears however that we may legitimatelydraw the following conclufions. In the firftplace the formation of nitric acid from animalmatter in putrefaction, i§ not owing to atmof-pheric air being prefented to the azot when ina nafcent ftate, for this change takes place afterthe azot and other gazefiable fubftances haveactually affirmed the elaftic form. Secondly,the elements of the putrid gas are carbonicacid, azot, hydrogen and carbon, not mixedbut combined together though weakly: thiscombination is in part deftroyed by mere wafh-ing in water, but more compleatly by the afitionof thofe alkaline bafes that are not compleatlyfaturated with carbonic acid; when the car-bonic acid is abftracted, the further decom-pofition of this gas by atmofpheric air tendsmore to the production of ammonia and car-bonic acid than of nitric acid. Wafhed chalkafter being thus nitrified often contains a littlenitrat of potafh as well as nitrated lime : it doesnot however hence neceffarily follow that pot-afh is alfo a produCt of putrefaCtion; for itmay poffibly pre-exift in the chalk in a ftateinfoluble in water, as it does in leucite, in thealum ore of La Tolfa, and other minerals. Theimportant prafticxl conclufion to be deducedfrom thefe experiments is that the only alkalinefubftance to be admitted in the compofition ofnitre beds is mild calcareous earth.

Chalk however is not only capable of beingnitrified by expofure to the combined actionof atmofpheric air and putrid gas, but alfoby means of the atmofpheric air alone. Onthis fubjeCt there are fome experiments byLavoifier and Clouet, much to the purpofe. cThe village of Roche Guyon on the Seine ,is fituated on a ridge of chalk, which havingthe charafter of nitrifying fpontaneoufly by ex-pofure to the air, was on this account vifitedand particularly examined by the able chemiftsjuft mentioned. In order to afeertain whetherthis chalk before the afition of the air con-tained any nitrous fait, feleCHon was made ofa part of the rock which had recently been laidbare by the falling down of a large mafs. Inthis newly-expofed face of rock, a gallery hadbeen driven, of which the further extremityhad been excavated only two or three daysbefore. In order to render the experiment asunexceptionable as poffible, about a foot moreof chalk was removed from the extremity ofthe gallery, after which a fpecimen of theweight of i2f lbs. was dug out, and fubjeCled

* Mem. Etrsng. dc l’Acad.dcs Sci. xi. p. 503.

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