ACI 



ACO 



but its effects on the negroes has been 

 pernicious. These trees cannot be pre- 

 served in England but with great care 

 and much heat. 



ACHROMATIC, an epithet expressing 

 a want of colour, introduced into astro- 

 nomy by De la Lande. 



ACHROMATIC telescopes, are telescopes 

 contrived to remedy the aberrations in 

 colours. They were invented by Mr. 

 John Dolland, optician. See OPTICS, TE- 

 LESCOPE. 



ACHYRANTHES, in botany, a genus 

 of the Pentandria Monogynia class of 

 plants, belonging to the natural order of 

 Miscellanese. There are eleven species, 

 but they have but little beauty, and are 

 only preserved in botanic gardens. 



ACHYRONIA,in botany, a genus of the 

 Diadelphia Decandria class and order: ca- 

 lyx five-toothed; the lower tooth elonga- 

 ted and cloven; leg'ume compressed, ma- 

 ny-seeded; one species, viz. A. villosa, a 

 shrub found in New Holland, with long 

 silky hairs : leaves lanceolate, acute, en- 

 tire, with silky hair round the margin. 



ACIA, in botany, a genus of the Mono- 

 delphia Dodecandria class and order : ca- 

 lyx five-parted, five petals, drupe dry, co- 

 riaceous, fibrous, one-seeded. Two spe- 

 cies,trees sixty feet high, found in GuiaR-a. 



ACICARPHA, in botany, a genus of the 

 Polygamia Necessaria class and order: 

 receptacle chaffy, the chaff uniting with 

 the seeds after flowering ; seeds naked ; 

 florets tubular ; calyx five-parted. One 

 species, found in Buenos Ayres. 



ACID, in chemistry, a term originally 

 synonymous with sour, and applied only 

 to bodies distinguished by that taste ; but 

 it now comprehends under it all substan- 

 ces possessed of the following properties. 

 Acids, when applied to the tongue, excite 

 the sensation of sour; they change the 

 blue colours of vegetables to a red ; they 

 unite with water in almost any proportion; 

 they combine with all the alkalies, and 

 most of the metallic oxides and earths, 

 and form with them those compounds 

 called in chemistry salts. Every acid does 

 not possess all these properties, but they 

 all possess a sufficient number to distin- 

 guish them from other substances. See 

 CHEMISTRY. 



ACID1FIABLE base, or RADICAL, any 

 substance capable of uniting, without de- 

 composition, with such a quantity of oxy- 

 gen as to become possessed of acid pro- 

 perties. Almost all the acids agree with 

 each other in containing oxygen, but they 

 differ in their bases, which determine the 

 species of the acid. Sulphur combined 



with certain portions of oxygen forms sul- 

 phurous or sulphuric acid, according to 

 the quantity of oxygen absorbed. 



ACIDOTON, in botany, a genus of the 

 Monoecia Polyandria class and order ; it 

 has male and female flowers on the same, 

 or a different tree. There is but one spe- 

 cies, viz. A. urens, a native of Jamaica, 

 which grows to the height of eight or 

 nine feet. 



ACIPENSER, a genus of fishes of the 

 order Cartilagenei : the characters are, 

 that the head'is obtuse, the mouth is un- 

 der the head,retractile, and without teeth; 

 that the four cerri are below the front, 

 and before the mouth ; the aperture of 

 the gills is at the side, the body is elonga- 

 ted, and angulated with many series of 

 scuta, or scaly protuberances. These may 

 be ranked among the larger fish ; are in- 

 habitants of the sea, but ascend rivers an- 

 nually; the flesh of all of them is delicious; 

 from the roe is made caviar, and from the 

 sounds and muscular parts is made isin- 



flass ; they feed on worms, and other 

 shes ; the females are larger than the 

 males. There are five species: A. sturio, 

 or common sturgeon, inhabits European, 

 Mediterranean, Red, Black, and Caspian 

 seas, and annually ascends rivers in the 

 spring. (See plate I. Ichthyology, fig. 2.) 

 A. schypa, inhabits the Caspian sea, and 

 large lakes of Siberia. A. ruthenus, and 

 A. stellatus, both inhabit the Caspian sea. 

 A. hufo, inhabits the Danube, WoJga, and 

 other Russian rivers, and also the Caspian. 

 The skin of this species is so hard and 

 tough, as to be used for carriage traces. 

 See STUHGEOX. 



ACNIDA, Virginia hemp, in botany, a 

 genus of the Pentandria Pentagynia class 

 and order. There is but a single species, 

 viz. A. cannabina, which is a native of Vir- 

 ginia, and some other parts of America; 

 it is seldom cultivated in Europe. 



ACONITUM, aconite, wolf's-bane, or 

 monk's-hood, in botany, a genus of plants 

 of the Trigynia order and Polyandria 

 class, and pertaining to the natural order 

 of Multisiliquje. In the last edition of 

 Linnaeus, by Gmelin, this genus compre- 

 hends fourteen species ; most of the spe- 

 cies of aconite have been deemed poison- 

 ous. The ancients were so surprised at 

 their pernicious effects, that they were 

 afraid to touch the plants; and hence 

 sprung many superstitious precautions 

 about the manner of gathering them. 

 Theophrastus relates that there was a 

 mode of preparing the aconite in his days, 

 so that it should only destroy at the end 

 of one or two years. But some have 



