182 Walsh's Notices of Brazil. 



edition of Henry,* in which the correction of the law is thus 

 stated : 



" ' The force of vapour from different liquids, varies at the same 

 temperature,'] and ' tlie variation of the force of vapour, from all li- 

 quids, is the same, for the same variation of temperature, reckoning 

 from vapour of any given farce ;' thus, measuring the force of all 

 liquids at the boiling point, by thirty inches of mercury, it is 

 found, that by losing 30° of heat from 212°, the vapour of water 

 loses half its force, and so the vapour of any other liquid, loses 

 half its force, by losing 30° of heat below its boiling point ; and 

 so on for any other increment or decrement of heat ;J this has 

 been experimentally established by Mr. Dalton." — [II. Vol. Ad- 

 denda, p. 42.] 



* Biot, in his Precis Elementaire de Physique I. 265, a work published about six 

 years before " the second English edition of Dr. Turner had appeared, or the work 

 of Dr. Thompson, or the eleventh edition of Henry," has the following paragraph 

 relative to this supposed law of Dalton : 



" Les experiences que fit M. Dalton sur I'alcool, rammoniac, ct la dissolution de 

 muriate de ch aux, lui parurent confirmcr ^galcment la loi prec^dente. Toutefois, jc 

 dois prevenir que des observations posterieures, faites par divers physicicns, ont de- 

 truit I'idee de g(5Rcraltic, ct dc rigucur qu'il lui avait attribute. Le docteur Ure, de 

 Glascow, a pubhc a ce sujet des recherches dont la precision parait ne gu6re laisser 

 de doute, et un jeune et habile chimistc francais, M. Despretz, a et6 conduit par un 

 autre voie aux menies consequences." '^^ 



t Thus, if water, alcohol, and ether, be exposed to the temperature of 220°, the 

 elasticities will be respectively 34.2, 80.2, 240, in inches of mercury. — True, but why 

 does Mr. SiilLinan associate this fact with the law in question, as if it formed a part 

 of the latter, and thus make Dr. Henry appear to confound things so essentially dis- 

 tinct 1 — Because the doctor happened to place them on the same page 1 



tWill Mr. Silliman inform us, in what respect the law thus corrected diflcrs from 

 that originally announced by Dalton ■? and if he admits, as we j)rcsumc he vnll, that 

 it differs in no respect, will he also inform us, whether he is speaking seriously or 

 jocosely, when he first lamely apologhesfor admitting into his/irst volume, an tn- 

 correcl law, and tlic next moment repeats identically llie same late, with the assur- 

 ance that it is a modification of the former'! If Mr. Silliman should be disposed 

 to treat the matter seriously, we advise him to examine again "the eleventh edition 

 <ri" liis Henry ; he will find that far from admitting the inaccuracy of the original law 

 of Dalton, Henry does not even notice the fact of its truth having l)een disputed. 



WALSH'S NOTICES OF BRAZIL. 

 We have selected the following extracts from that very 

 amusing and instructive work, " Notices of Brazil, by the Rev. 

 \\. Walsh." 



"In nrazii, all journeys arc suspended at the Ave Maria, that is, the ves- 

 pers to the Viffrin, that commence after sunset, instead of a curfew, this 



