A T O 



A T O 



ATHEROSPERME^, a new natural order, thus (late are aU multiples of the fame unit whirl, nn« i. .« 

 denominated from its leading genus. See the laft article, fidered as hyHrogen. ' "** " ^•'"• 



Brown Bot. of Terra Auftr. 21. Dr. Prout's efTay is terminated ver>' abruntlv and ' 



Floioers either feparated or united. Calyx of one leaf; evidently imperfeft. The above views are not exolictlv 

 Its margin divided into a generally doub e row of fegments, ftated in the paper alluded to, though it is obvious thev are 

 the mnermoft, fometimcs all of them, half petalJike (or in- what the author had in view; and as they have b 

 ternally coloured). There are alio in the female, as weU as recently adopted by Dr. Thomfon, in the new edition^of 

 in the united, flowers, fmall, internal fcales, at the bafe of his Syflem of Chemiftry, which may be viewed in the lieht 

 thefe fegments. Corolla none. Stamens m the male flowers of a national work, we confider it our duty to lay a bncf 

 numerous, inferted into the bottom of the calyx, with accef- account of them before our i-eaders. 



fory fcales ; in the united flowers they are fewer, and in- The fird of the above points attempted to be eftablid.ed 



ferted into the throat ; anthers attached by the back, of two by Dr. Prout has been already difculTed at fome lenrth in 



cells, each cell opening by a longitudmal valve, feparating the articles Proportion-.s, Definite, and Theory, Atomic 



from the bafe upwards. Germens one or more, generally an Indeed, we believe it is very generally admitted by all" 



indefinite number, with a fingle, ereit germ ; fiyles folitary, thofe chemifts who have taken the pains to examine and 



occafionally lateral, or from the bafe ; figmas fimple. think upon the fubjcft. It is chiefly founded upon fads 



Seeds, (termed feed-like pericarps by Mr. Brown,) awned and reafonings, whicli few at prefent' affedt to doubt, and 



with the feathery ftyles, and enclofed in the enlarged tube of of which the following is a fummary. i. Bodies 'unite 



the calyx ; embryo ereft, fhort, in the bottom part of a foft together in certain definite proportions by weight, that is 



flefhy albumen. The feveral fpecies are trees, with fimple, certain weights of fome bodies always combine with certain 



oppofite leaves, deftitute oijlipulas. Stalks axillary, fingle- weights of other bodies. This conftitutes the bafis of the 



flowered. atomic theory, or the theory of definite proportions, as fome 



Juffieu it feems, Ann. du Muf. v. 14. 116, has efi;ablifhed have chofen to term it. 2. Subilances in a gafeous ftate 



an order termed Mommies, in which Atherofperma is in- have been demonflrated to combine with reference to their 



eluded, along with Pavonia of Ruiz and Pavon, its near buli or -volume, that is to fay, one volume of one gas always 



ally, and the Ambora, (fee Mithridatea,) Monimia, and combines \Tith one or more fimilai- volumes of another and 



Ruiza, which three lafl; Mr. Brown confiders as conftituting not with any odd fractional parts. Moreover, the volume 



the genuine order of Monimieit, and therefore he has pro- or bulk of the refulting compound, if it happens to be a 



pofed the above, of which a mofl; eminent diftinftion is their gas, always bears a fimilar relation to the original volumes 



having the valvular iinz/jfrj' of the Lauri. ( See that article. ) of its component gafes. For thefe important laws we are 



This feparation is confirmed by two New Holland plants indebted to Gay Luflac, and they confl:itute the bafis of 



evidently of the fame family, but which have xmAeAfioivers, what has been denominated the theory of volumes. 5. It is 



a fl;rufture not probable m Monimieir. The place oi Athe- univerfally admitted, that the yam? weights of the /amf refult- 



rofpermeif, in a natural feries, is difhcult to fix. Though fo ing compounds are formed when bodies unite in a gafeous 



widely different, in moft parts of their ftrufture, from Lauri, ftate according to their volume, as when they unite in any 



(now called Laurinn,) they agree in anthers, and very re- other manner according to their weight ; thus, for example, 



markably with fome of them in fenfible qualities. Pavonia one volume ( 100 cubic inches) of muriatic acid gas will unite 



above-mentioned cannot, by Mr. Brown's account, be fepa- with one volume ( 100 cubic inches) of ammoniacal gas, and 



rated from Atherofperma, diff'ering merely in the oblong form the fame weight of the fame compound, (muriate of 



form, and regular burfting, of its female calyx ! Its quali- ammonia,) as if 39.183 grains (the abfolute weight of too 



cubic inches) of muriatic acid, united with 18.003 g""'* 

 in the year 1810, 556 inhabit- (the .ibfolute weight of 100 cubic inches) of ammonia; 



the two numbers 39.183 and 18.003 being to one anothei* 

 Col. 4, 1. 3 from as 1.278 : .5900, or as 37 : 17, the fpecific gravities and 

 )f an inch. the weights of the atoms of thefe two fubftances refpeftively. 



ATMOSPHERIC Air, Chemical Compufttion of. See Such is a brief llatement of the fads ; and it is argued that 

 j\ji{. if the above data are correft, it follows irreiiilibly from 



ATOMIC Theory, in Chemiftry. This important them that the lueights of the atoms of bodies, are to one 

 theory, which has added new luflre to chemiftry by raifing another as the fpecific gravities of the fame bodies in a 

 it to the rank of a mathematical fcience, was entirely un- ftate of gas ; and confequently that the theory of volumes 

 known when the earlier volumes of the Cyclopaedia were and the theory of atoms is one and the fame thing, dif- 

 publiflied. The hiftory of its origin and progrefs has ^rent fets of numbers only being employed. Some appa- 

 been amply detailed in fubfequent parts of the work, par- fent deviations from this law, which however cannot be 

 ticularly under the articles Proportions, Definite, Sim- 



ties are the fame 



ATKINSON, 1. 3, r. 

 ants. 



ATMOSPHERE, Weight, tfr. of the. 

 the bottom, for half an inch r. T'gth or .02 of an inch. 



PLE Bodies, and Theory, Atomic; fo that we have Httle 

 left to add here, except a brief fummary of fome recent 

 modifications fuggefted by Dr. Prout, and fubfequently 

 adopted by Dr. Thomfon. See an anonymous EiTay on 

 the relation between the Specific Gravities of Bodies in 

 their gafeous State, and the Weights of their Atoms, 

 vols. vi. and vii. of Thomfon's Annals of Philofophy. 



The objeft of Dr. Prout in the above eflay is to 



by any means confidered as exceptions, will be noticed 

 hereafter. 



With regard to the fecond point contended for by Dr. 

 Prout ; namely, that the fpecific gravities of all bodies in 

 their gafeous ftate, or, in other words, the weight of their 

 atoms are multiples of the fame unit or hydrogen ; it is 

 partly founded upon experiment and reafon, and partly (at 

 prefent at leaft) upon hypothefis. The following is a 

 fummary of the grounds upon which the opinion has been 



fhew, ift, that the theory of volumes fuggefted by Gay fo'"™^'!;, , ., . . . , ,. 



Lufl-ac, and adopted by Berzelius and fome others, is i- The fpecific gravity of .immon.acal gas, according to 



abfolutely identical with Dalton's Theory of Atoms; and ftr Humphry Davy, is .590164, common air being i.ooo; 



2dly, that the fpecific gravities of bodies in their gafeous according to Biot and Arrago, it is a fraftion greater : 



hence 



