542 



Exp€rimmts to ascertain the 



fJan. 1 , 



in his power to produce any proof. In 

 the public papers, therefore, which was 

 all the refourcc 1 kad at that time, I de- 

 nied tiie charge, and called upon him 

 for the pro(^f of what he had advanced ; 

 at the fame time fendin;; him the newf- 

 paper in which this was contained : but 

 he made no reply. In my preface to a 

 F;iil Sermon in the year folluwini;, 1 

 therefore faid that it fuliiciently appeared 

 that '* he iiad neither ability to main- 

 tain his cliaiwe, nor virtue to retratt it." 

 This alfo was conveyed to him. An- 

 other year having eUipfed without his 

 making any reply, I added,, in the pre- 

 face to another feniion, after repeatini: 

 ivhat 1 had laid before, " A year more of 

 filciice on his part iiaving now elapfed, 

 tliis is become more evident thau be- 

 fore." This alfo he bore in iilence, 



A cireuinftance that fliovvs pcculia? 

 malignity was, that on the breaking out 

 «f the riots of Birmingham a perfon 

 *ho at that time lodgcrl in the fame 

 iioufc with him at Margate, informed jue 

 that he could not contain his joy on the 

 occalion ; but that, ruiming from place 

 to place, he exprefl'ed it in the moll un- 

 equivocal miumer. 



After this I never licard any thing con- 

 cerning Mr. Burke, but from his publi- 

 <;ations, except that I had a pretty early 

 and authentic account of his firjl peu- 

 Jion, which he had taken fome pains to 

 conceal. Such is fometimcs the fate of 

 tiie moll promifmg, and long continued, 

 of luiniuH friendlhips. But if I have; 

 been difappoiuted in ibmc of them, T 

 buve derived abundant falisfadtion and 

 advantage from others. 



J. Priestley. 

 Nort/ntmherlatid, Fc[>. 1, laiM, 



i'l) l/ie Editor of the Monthli/ Magazine. 



SIR, 



irp^IlE names of Humboldt and Gay- 

 X Lurtiie are too advantagcoufly known 

 to tiie public, as al)le ntituralills and in- 

 defatigable chcmilis, to rot|utrc that 1 

 ■fliould oiler any ajjulogy for tranfmitting, 

 with a view to infertion in the Monthly 

 Magazine, the following iliort account of 

 fome new experiments lately made by 

 tlieni, in order to afcevlain, with greater 

 pieciilou tiuiii Imd hitherto been done, 

 the propoitions of the component priuci- 

 pleii of atniofplieric air. 



The alkaline fulphnrets have been long 

 «>mployed as eudiometers, from a belief 

 that they abforb oxygen alone, without 

 haviijg the leafc alhnity for ayotc; but 

 »hvs oiiiuion is now fouiid to be errone- 



ous, as thefe fulphnrets, when heated, 

 abftjrb a portion of azote, as will Wc fecii 

 froiO' the following experiments. 



The illuflri(jus cheuiifts above mention- 

 ed took two Hulks of unequal capacities, 

 into which they puf. equal quantities of 

 heated lulphuret. At the terniina'ion of 

 ten days,, the abforption m the fniajl llalk 

 was '22, 5, and tn the hirge one 'MY, (i. 

 They next expofed pure azote to the ac- 

 tion of an alkaline Uilphuret, beateil to- 

 ebullition, in whicii cafe a confiderable 

 jjortion of the a/ote was abforbed ; but 

 when a folution of the liune fulphuret was 

 ufed cold, !is is always done by M. Ber- 

 thollctt, no abforption of azote took. 

 ])liice, at leaft not in a fenfdjle degree. 



Humboldt and his utfociate, neverthe- 

 lefs, give the preference to the eudiome- 

 ter of \'oltiv, wliich it is well known cou- 

 ijfts in detonating hydrogen w ith atiuo- 

 fpheric air, by means of the electric fpark. 

 The refult of their numerous experiments, 

 indeed, fully prove that this is the bell 

 method of afcertaining the exact quantity 

 of oxygen contained m atmofpheric air : 

 they obferved, liowever, in the courle of 

 their experiments, fome phenomena it 

 ■was difficult to explain. 



On mixing 100 parts of hydrogen, witlt 

 200 of oxygen, and inllaming them hy 

 means of the elettric fpavk, the ablbrp- 

 tion was 146. 



'I'he fame abforption took place on 

 mixing the 100 parts of hydrogen, with 

 300, -ioo, or even 900 parts of oxygen. 



On the mixture of 100 parts of hydro- 

 gen, with an equal quantity of oxygen, 

 the abforption was .55. 



One hundred parts of hydrogen, mixed 

 with l(j00 of oxygen, did not detonate. 



The other gall'es exhibited the fame 

 dilVirences. 



More nmnerousc, xperiments, however, 

 convinced thcl'e chcmills, that 100 parts 

 of oxygen, require for its compk-lc liitura- 

 tion '200 parts of hydrogen; whence they 

 conclude, that in the preceding experi- 

 mrnti* the hydrogen had not been wholly 

 inHamed; and that this circumllance had 

 occalioncd the refults which appeared to 

 tlicm fo i'urpriling. 



They now proceeded to afcertain, 

 whether the product of the combiiltioii 

 of hydrogen and oxygen, was uniforndy 

 pure water, or if it contained acid. The 

 relali of thefe experiments was, that wa« 

 ter fo obtained is perfetrlly pure. 



They next inilituted a vaft number of 



experiments, in order to determine the 



refpettive quantities of oxygen and liy- 



drojjen coiumncd ia this water, and "af- 



cert»iiie<i 



