-as 



THE CIVIL ENGINEER vVNJ) AKCHITECT'S JOURNAL. 



[November, 



exporiiiu'iits of the liittcr :iri- dated Iroiii tlic sninnuT of 1781. A coniiiui- 

 nifiitiou of I'liestley is (|Uotfd witlioiit dftoniiiiiiiif;- tlif date, willioiit 

 spcaUing of tlic coiii-Iiisioii.s and without rvcii sayiiii,' wlieii tljrsc coiiclii- 

 sioiis occiined to C'avoiidisli. Tliis nuist lii' consideivd as a most mateijal 

 omission. 



4tli. Ill nnc of liln,u:iU'n's additions to the paper, Cavendish's conclusion 

 is ivlalcd ill tlicse leinis, oxygen gas is water deprived of its phlogiston; 

 this addition is ]iostcrior to the arrival in England of Lavoisier's jiaper. 



It may be farther observed that in another addition to Caveiidislis paper, 

 written by the hand of tliis chemist, and wliicli is certainly later tliaii t)ie 

 arrival in England of Lavoisier's paper. Cavendish establishes distinctly for 

 the first time, and as the hypothesis of Lavoisier, that water is comjiosed 

 of oxygen ;md liydrogen. J'erhaps no essential difTercnce can be found 

 between tliis conclusion and tliat at which Cavendish had at first arrived, 

 that oxygen gas is water devoid of its phlogiston, for it is sufficient to make 

 ibem identical to consider phlogiston as liydrogen, but to say that water is 

 coni))osed of oxygen and hydrogen, is certainly to come to a clearer and less 

 eqiiivoeal conclusion. I may add that in the original part of his pa]ier, in 

 that which was read before the Kojal Society before the arrival of Lavoi- 

 sier's jiaper in England, Cavendish thouglit it juster to consider inflammable 



air as " as water plilogisticated, ratlier than as pure ))lilogistoii." p. I-JO. 



Let us now see what was Watt's |)art, in \vliich dates will play a very 

 important cliaracter. It ajipears that Watt wrote to Dr. Priestley on the 

 a;tli April, 1783, a letter in which be discaiited on the experiment of iii- 

 Jianiing two gases in close vessels, and that tlien he came to the conclusion 

 that " water is composed of dephbigisticated air, and of phlogiston, both 

 dejirived of a part of their latent heat*. 



Priestley deposited the letter in the bands of Sir Joseph Banks, re- 

 questing him to have it lead at one of the next meetings of the Royal So- 

 ciety. \\'att then desired that this reading should be jiut off, in order that 

 lie might have time to see how far his theory agreed with the recent expe- 

 riments of Priestley: at last this letter was not read until A]iiil, 17S4.t 

 This letter Watt alludes to in a paper addressed to Deluc, dated the -Jlith 

 November, 17831; many new observations and new reasonings appeared 

 in tliis paper, but almost all of the original letter was preserved, and in 

 printing, it was distinguished by the addition of reversed commas ; in tlie 

 ]>art thus marked, is to be found the important conelnsioii and notes above. 

 We read further, tliat the letter was communicated to several members of 

 the Iioyal Society when it was received by Dr. Priestley in April, 1783. 



In Cavendish's paper§ as it was at first read, there is no allusion to 

 Watt's tlieory; an addition posterior to tlie reading of the letters of this 

 latter, and written entirely in Cavendisli's hand, mentions this theory. 

 Cavendish, in tliis addition, shows the reasons, which lie thought he had not, 

 to complicate liis conclusions, as Watt had done, witli considerations rela- 

 tive to latent heat. It leaves in doubt the (juestion, whether the author 

 were acquainted with Priestley's letter, of April, 1783, or whether he only 

 sawtheletterdated the 'JGth of November, 1783, and read the '29th of Ajiril, 

 1784 ; upon wbieh it is important to observe, that the two letters appeared 

 ill tlie Philosophical Traiisaetions, thrown into one. The letter to Priestley, 

 of the 2(jtli of April, 1783, remained sometime (two months after the jiajier 

 of Watt) in the hands of Sir Joseph Banks, and other Members of the 

 Koyal Society, during the spring of 1783. This is what appears from the 

 circumstances mentioned in the note at page 330. It seems difficult to 

 suppose that Blagden, Secretary to the Royal Society, did not see the 

 )iaper. Sir Joseph Banks must have given it to him, since it was intended 

 to be read at the meeting. i| We may add, that since the letter was ]iie- 

 served in the records of the Royal Society, it was under the caie of Blagden, 

 the Sei retary. Could it be possible to suppose that the jierson wliose'haud 

 wrote the reniaikable passage, already quoted, relative to a coinimiiiication 

 made to Lavoisiei, in June, 1783, of Cavendish's conclusions, would not, at 

 least, have informed Cavendish that Watt had arrived at the .same coni'lu- 

 .sions, at farthest, in Ajiril 1783. Tliese conclusions are ide:itieal, with 

 the single difference, that Cavendish calls ile|ilogisticated air, water deprived 

 of its phlogiston, and that Watt says that w ater is composed of dephlogis- 

 ticaled air and plilogiston. 



We must rem.irk that in Watt's theory, there is the .same uncertainty and 

 vagueness, that wc have already found in those of ( avendish, and that 

 all this occurs from the use of the term, not exactly defined, of jihlogiston.U 



_' Wc c.'in, with ItiU ciiiiliflcnce, (It-dufe froiii Iliu unpiiblislii:il ronospuiultiu-c ot 

 Walt, Ihal lie luul already loniiL-d liis llietny ut' llie coinposiliuli of walor, in December, 

 1780, and in-obably J-ooncr. Besides, PriesUey declares, in ids paper, ol" tile 2SlIi April, 

 178a, llial, before liis own experiments, Walt was atlaelied to Uic idea llial t!ie sleaiii of 

 Avaler coidd be Iransforined into permanent gases, fp. 410.) 



\VaU liiinself, in liis p.ipei-, (p. 33.*),) declares dial, for some years, lie Iiad bci n ol 

 opinion lliat air is only a inodificalion of water; luid he gives a detailed .ii-coiint ot llie 

 txpelilneiits, and le.nsoningson «liich tliis opinion is founded. - J\'t,te of Mr. M'att, juri. 



+ Priesllcj 's letter was read on llie anih of April, 178-1. 



i Williout any dunbt the Ccnevesp philosopher, then in London, received it ill Ibal 

 time. It lemaineil in his bands unlil the time llial Walt heard of Caveiiilish's paper 

 linving been le.iri before llie Koyal Society. From that lime mv father took insianl 

 measures to have his paper addressed to Deinc, and his teller 'to Dr. Priestley, of 

 the 201h of April, 1783, imiiiediaiely read before the Royal Society. Tliis reailiiiL', 

 loqniied by Walt, of the paper addressed lo Deliic, took place on the 29lh of April, 

 nti\.—Aole of Mr. JIatl.jim. 



ti Philosophical ti ansaclioiis, 1784, p. 140. 



II I'hilo-opliical tniiisactioiis, p. 300. 



II In a note of bis paper, of the 211111 November. 1783, (p. 331,) is lo be read lliis note 

 of Wall: " Anteriorly to llie expelilnenls of Dr. Priestley, Kirwan hail pioved, by in- 

 jenious dednclions, borrowed lioni oilier faels, Ihat inllanimable air is in all probability 

 true pblowisloii iiiiiler an aeiial form. Kirvvan's ari;iiments do not seem, l.i mr. peiliclly 

 conviniiinu, but it appears nincli belter to ■ellle the point of the ijiiesli.iii lb) direct ex- 

 perinienl." Note of Mr. lf'utt,jiw,'fiii:^Ji 



With Cavendish, it cannot be di'termiiieil. wlietber |dilogiston means simply 

 inllaiiiinalile air, or whether thai chemist was not rather iniliiied lo consider 

 as inllaininalile air, a combinatiun of water and ])hlogiston. Watt .says ex- 

 jircssly, even in his jiaper of the "itJtli November, 1783, and in a passage 

 wliieh is not a part of his letter of April, 1783, that iuHammable air, in his 

 opinion, contains a small quantity of water, and much elementary heat. 



These expressions on the jiart of two men so eminent, must be considered 

 as the mark of a certain hesitation touching the compositidii of water. If 

 Watt and Cavendish held the jirecise idea tliat waler lesulted Ironi the 

 re-union of two gases deprived of their latent lieat, ftom the re-union of the 

 bases of iuHammable and dephlogistieatcd air; if this conception was as 

 clear in their mind as it was in that of Lavoisier, they would certainly have 

 avoided the uncertainty and obscurity which I ha^•e iiointed out.* 



As to what relates to Watt, these are the new facts which we have just 

 established : 



1st. There is no jiroof that any one gave, before Watt, and in a written 

 document, the actual theory of the composition of water. 



■Jnd. Watt established tliis tlieory during the year 1783, in terms more 

 distinct than Cavendish did in his paper of 1784. By iutroduciiig the dis- 

 engagement of latent heat as a part of the process. Watt added to the clear- 

 ness of his couceiition. 



3rd. There is no proof; there is not even any assertion that the results of 

 Cavendish's theory ( Blagden calls it bis conclusion ) were coininunicated to 

 Piiestley before the ]ieriod, at which Walt informed him of his opinions in 

 bis letter of 2()th .-Xiuil, 1783. For a still stronger reason, nothing can 

 make us sujipose, particularly after reading Watt's letter, that this engineer 

 ever learned anjtliing relative to the composition of water, either from 

 Priestley, or from any one else. 



4th. Watt's theory was known to the Fellows of the Royal Society, 

 of several months before Cavendish's conclusions were ]iut upon paiier, ioid 

 eight months before the presentation of this chemist's paper to the Royal 

 Society. We can e\'en go farther and deduce from the facts and dates 

 before our eyes, that Watt first spoke of the composition of water, and that 

 if any one preceded hiin, we have no proof of it. 



5tli. In tine, a repugnaiiee at abandoning the doctrine of phlogiston, a sort 

 timidity at separating from an opinion so long established and so deeply 

 rooted, prevented Watt and Cavendish from doing complete justice lo ilieir 

 own theory ;t whilst Lavoisier, who had bioken these fetters first, present 

 the new doctrine in its full perfection. 



It might be very possible that, without knowing anything of each other's 

 labours. Watt, Cavendish, and L;ivoisier had, about the same time, taken the 

 great step of concluding from experiment, that water is the iiroduce of the 

 combination of the two giises .so often quoted, which is, in fact, with more 

 or less jiieciseness, the conclusion to which the three philosophers have 

 come. There now remains the declaration of Blagden, according to which 

 Lavoisier had received a coinmunication of Osivendisb's tlieoiy, even before 

 having made his chief experiment. This declaitition Bhigden inserted in 

 the very ]iaper of Cavendish ; I it appeared in the Philosophical Transac- 

 tions, and it does not seem that Lavoisier ever contradicted it, however ii-re- 

 concilable it might iqipear with his own account. 



On the other hand, notwithstanding all Blagden "s siisceiitibility abouc 

 Cavendish's pi iority, there is no \\"hete. on his Jiait, the slightest allusion 

 that may lead us to conclude that, before publishing his paper. Watt had 

 heard of that ot his competitor. 



We cannot affirm too strongly, relative to the question, whether Caven- 

 dish had any knowledge of SVatt's labours before drawing up the conclu- 

 sions of his own paper. To maintain that Cavendish i\as unacquainted 

 with Watt's conclusions, it must be remarked how inqirobable it is that 

 Blagden and others, to whom his conclusions were known, never spoke to 

 him about it. It might he farther said that Blagden, even in those parts of 

 the paper written with his own hand, and inlended to claim the priority tor 

 Watt, no where asserts lhat Cavendish's theory was conceived before the 

 month of April, 1783, although, in another addition to bis friend's oiiginal 

 paper, there is a quotation relative to Watt's theory. 



Since the question of knowing at what epoch Cavendish came to bis con- 

 clusions, is envelope d in great obscurity — it will not be useless to investigate 

 what was the practice of this chemist when he coinmunieated his discove- 

 ries to the Royal Society. 



• 'I'be nbscuiily in the iheorelieal conceptions of Watt and Cavendish, complained of 

 by Lord Brougbam, do not seem, to mc, lo be well founded. In 17S4 llicy knew how 

 lo prepare two jiennancnt gases, very dissimilar Ironi e;u li oilier. These iwo gases, 

 some called bxed and inllanimable air; and others, depblogistieated air and phlogiston; 

 others, in tine, o\\geii and hylrugen. By the coinbinalion of depblogislicated air and 

 pbiogislon, w.is produced water"^ having a weight equal lo Ihit oi the two gases. 

 Waler, from llial lime, was no longer considered a simple body ; bnl was composed ot 

 (iephlogislicatcrl air and phlogiston. The chemist who drew this consequence may 

 h.ive liad lalse ideas as 10 Ihe inlimalc naUiie of plilogiston, wiilioiil, Ihal in the least 

 degree, throwing any nncertailily on the nieiil of his brsl riiscovei^u in tlie pieseli- 

 day, it has been iiiathematically demoiistratetl lhat liydrogen or phlogiston is an element 

 lary body; that ilisnot .is Watt and Cavendish believed, for a time, the coinbinalion of 

 a radical and a liille water— jVo*e of M. Arago. 



1 No one ciiiild expect llial Walt, writing and publishing for the first lime, engagcil 

 in Ibe c;ires of an imnitiise establisliinenl, and commercial atlairs equally extensive, 

 coiihl contend against the eloquent and practised pen of Lavoisier; but the sketch ol 

 his theory (see page 331 of bis paper) appears lo me, who, I iiuisl confess, am not an 

 miparlial judge, as Inininoiis and as expressive, as llu- cunclnsions of the illusnioiis 

 French chemist. — Ao/e of Mr. fl'tilf. juu. 



i A letter lo I'lOfessor'Ciell, in winch Blagden gives a delailed descriplion of ihe 

 discoveij, ap]>eais in llie ..tniio/cM for l7.Sli. Il Is reiiiai kabl.-, lhat in Iliis bller lila'deii 

 says be ciininiiiiiicalcd lo I.ivoisiir llie opinions ol Civendisb and II all. anil lliat'tliis 

 laller ii.inie appear-, for the brsl lime, in llic re. ilal ol ihe veibal conlidences of the 

 becretaiy of llie Ro)aI Sociely.— A'o/c of Mr. II al/,Jiin. 



