A G A 



to the effcfts of mnfs, though at firll fight there appear to 

 be fome circumftances favouring the opinions of BerthoUet 

 refpefting its influence in chemical operations, yet we can 

 by no means agree in fuppoiing its influence fo great as 

 reprefented by that eminent chemift. No quantity of 

 water, for example, would decompofe fulphate of mag- 

 nefia, though the affinity of fulphuric acid for water is 

 very great, and though the infoluble nature of magnefia 

 would, according to Berthollet's views, favour the union of 

 tlie water with the -acid. ALifs here, therefore, either does 

 not operate at all, or very feebly ; and there are numerous 

 ■nalogous inftances, weU'known to every chemiit, to which 

 the fame remarks are equally applicable. 



Again, it has been fufficiently eftablilhed, that gafes 

 unite with reference to their volume, and cannot be made to 

 unite in intermediate proportions, even although the refult 

 of their union be likewife a gas. Thus, for example, one 

 volume of chlorine gas and one volume of hydrogen gas 

 unite together, and form, without any condenfation, or 

 other apparent phyfical change, two volumes of muriatic 

 acid gas, nor can they be made to unite in any other propor- 

 tions. Here then is an example of chemical union, in 

 which the effefts of ma/s and mode of exi/lcnce are quite out 

 of the queition. 



From thefe, and particularly from many recently efta- 

 blifhed fafts, we think it proved beyond a doubt, that the 

 power which determines bodies to combine in certain pro- 

 portions is a property inherent in the original caufe of their 

 union, and confequently is a power totally different from that 

 exerted by mafs or other external circumftancc, though it is 

 not perhaps altogether independent of their influence. For 

 further information, we refer our readers to fir Humphry 

 Davy's Elements of Chemical Philofophy, where, befides 

 an excellent account of the fubjeft in general, they will 

 find a mafterly refutation of Berthollet's doftrines. 

 'AFORE, 1. 2, for ftem r. ftem ; 1. 4, ditto. 



AFZELIA, in Botany, (fee that article,) is Gerardia 

 caJJioiJcs, Purfti 424. (G. Afzelia ; Michaux Boreal.-Amer. 

 v. 2. 20. Anonymos caffioides ; Walt. Cai-olin. 171.) — 

 " Panicled, with wand-like branches. Leaves pinnatifid, 

 with linear briftlc-like fegments." — In dry fandy woods of 

 Garohiia and Georgia. Annual, flowering in July and 

 Auguft. Flowers fmall, yellow. PiirJ/:. 



Afzelia, Sm. Tr. of Linn. Soc. v. 4. 221, fo named in 

 honour of its difcoverer, Adam Afzelius, M.D. Demon- 

 ttrator of Botany at Upfal, author of feveral diflertations on 

 Swcdifh Rofcs, and of other learned botanical treafifes, is a 

 very noble genus, of which we have long expefted from Dr. 

 Afzelius himfelf an illuftration of the fpecies. They are all 

 natives of Sierra Leone. — Clafs and order, Decandr'ia 

 Monogynia. Nat. Ord. Lomentactx, Linn. Legumhwfe, 

 .lufl". 



Eff. Ch. Calyx tubular ; limb in four deciduous feg- 

 ments. Petals four, with claws ; the uppermofl very large. 

 Two upper ilamens imperfeft. Legume with many cells. 

 Seeds with a tunic at the bafe. 



This genus confifts of trees with large, fraooth, abruptly 

 pinnate, altertate haves. The^oiuers areracemofe, crimfon, 

 with fmall braSeas. Legumes woody and ponderous, fmooth, 

 ovate, acute. Seeds near an inch long, parallel, ovate, black, 

 the lower half of each invefted with a flelhy tunic, of a bril- 

 liant permanent fcarlet, and a rather waxy appearance. The 

 r.ative Africans remove this tunic, and ufe the feeds for- 

 beads. 



AGASTACHYS, from ayaro,-, remariahk, and Tx-x^h 

 a fpiiti alluding to the abundance of iu fpiked flowers. — 



A G G 



Brown Tr. of Linn. Soc. v. 10. 15H. Prodr. Nov. HolL 

 V. I. 37 I. — Clafs and order, Tetrandrla Monogynia. Nat. 

 Ord. Pnlcaceit, .Tuff. 



EfT. Ch. Corolla regular, of four petals, cohering at the 

 bafe, bearing the ftamens in the middle. Filaments diftinft. 

 Neftary none. Germen feflile, triangular, fingle-feeded. 

 Stigma unilateral. 



I. A. odorata. Fragrant Agaftachys. Br. n. i. — 

 Found in the fouthern part of Van Diemen's idand, near 

 Adventure bay, by Mr. David Nelfon, and afterwards by 

 Mr. George Caley. A Jhrub, perfeftly fmooth in every 

 part. Leaves fcattered, entire, flat. Spikes numerous, 

 fimple, terminal, as well as axillary from the upper leaves. 

 Flonvers alternate, feflile, with a folitary, hooded, permanent 

 bradea to each. Corolla yellowifti, deciduous. PiJI'l 

 fhorter than the Jlamens. The fruit has not yet beer- 

 examined. Brown. 



AGATE, col. 2, 1. 15. They are conveyed from 

 Germany in blocks ; and cut by means of diamond powder 

 into leaves for making caps for the pivots of mariners' needles, 

 and other purpofes. 



AGATHARCHUS.in Biography, a painter of the ifle 

 of Samos, who is faid to have been inftrucled by jEfchylus 

 in the art of introducing perfpeftive into the decorations of 

 theatres, and to have been the firfl; who wrote on this fubjeft, 

 and communicated the ait to Democritus and Anaxagoras. 



AGDESTIS, in Botany, a fanciful name, adopted by 

 De CandoUe, from the authors of an unpublirtied Mexican 

 Flora, whom he cites as M09. and Seflc. It is apphed to a 

 doubtful genus, related to Menifpermum, and perhaps a fort 

 of lufus nature, having ftamens and piftils in the fame flower, 

 which is almoft unexampled in this tribe. The above deno- 

 mination is that of a fabulous monfter, faid to have been male 

 as well as female, and produced by Jupiter from the ftone 

 Agdos. This genus therefore being not clearly underftood, 

 and as yet very little known, may hereafter be abolilhed as 

 well as its name. — Clafs and order, Polyandria Monogynia. 

 Nat. Ord. Sarmentacen, Linn. Menifperma, JuflT. Menif- 

 permete, De Cand. 



Efl". Ch. Calyx inferior, of four leaves. Petals none. 

 Filaments thread-ftiaped. Anthers oblong, cloven at each 

 end, incumbent. Germen and ftyle with four furrows.' 

 Stigmas four, fpreading. Capfules four, combined. 



I. A. clematidea. Bowery Agdeflis. — Native of New 

 Spain. A fmooth fhrub, with a branched, twining, round, 

 ftriated Jlem. Leaves alternate, diftant, ftalked, exaftly 

 heart -(haped, entire, pointed ; their lobes very obtufe. 

 Flowers reddifh, corymbofe, axillary and terminal ; their 

 ftalks three-cleft. Fruit unknown. This plajit appears 

 very nearly akin to Clematis. 



AGGREGATjE, the title of the 48th order in Lin- 

 nseus's fragments of a natural fyilem, placed between the 

 Stellata and Compo/ita. (See Aggregate.) This is a 

 very mifcellaneous and ill-defined order, of which it is by no 

 means eafy to feize the idea, much lefs to give any definition, 

 or diftinftive character. Vaillant firft laid the foundation 

 of this order, in the Memoires de I'Acad. des Sciences for 

 1722. " The natural order oi Aggregate,'' fays Linnaeus, 

 Priel. in Ord. Nat. 528, " was firfl invefligated by Vaillant, 

 in the Mem. de I'Acad. des Sciences. They ?gree with 

 the Compofitic in having generally a common calyx as 

 well as receptacle, coDefting together many feffile florets, 

 each of which has always an inferior germen. But 

 there is a total difference v/ith refpeft to the remaining parts 

 of fruftification, nor can thefe two orders be, by any means, 

 united. The calyx, as aboie faid, is common to many 



flowers, 



