AVOGADRO, AMEDEO, CONTE DI QUAREGNA (1776-1856), Italian physicist, was born at Turin on the 9th of June 1776, and died there on the 9th of July 1856. He was for many years professor of higher physics in Turin University. He published many physical memoirs on electricity, the dilatation of liquids by heat, specific heats, capillary attraction, atomic volumes &c. as well as a treatise in 4 volumes on Fisica di corpi ponderabili (1837-1841). But he is chiefly remembered for his "Essai d'une manière de déterminer les masses relatives des molécules élémentaires des corps, et les proportions selon lesquelles elles entrent dans les combinaisons" (Journ. de Phys., 1811), in which he enunciated the hypothesis known by his name (Avogadro's rule) that under the same conditions of temperature and pressure equal volumes of all gases contain the same number of smallest particles or molecules, whether those particles consist of single atoms or are composed of two or more atoms of the same or different kinds.
AVOIDANCE (from "avoid," properly to make empty or void, in current usage, to keep away from, to shun; the word "avoid" is adapted from the O. Fr. esvuidier or évider, to empty out, voide, modern vide, empty, connected with Lat. vacuus), the action of making empty, void or null, hence, in law, invalidation, annulment (see Confession and Avoidance); also the becoming void or vacant, hence in ecclesiastical law a term signifying the vacancy of a benefice—that it is void of an incumbent. In general use, the word means the action of keeping away from anything, shunning or avoiding.
AVOIRDUPOIS, or Averdupois (from the French avoir de pois, goods of weight), the name of a system of weights used in Great Britain and America for all commodities except the precious metals, gems and medicines. The foundation of the system is the grain. A cubic inch of water weighs 252.458 grains. Of this grain 7000 now (see Weights and Measures) make a pound avoirdupois. This pound is divided into 16 oz., and these ounces into 16 drachms.
Avoirdupois Weight.
| Drachm, | 16=ounce, | 16=pound, | 14=stone | 2=quarter, | 4=hundred, | 20=ton. |
| 27.3 grains | 437.5 | 7000 | 98,000 | 196,000 grs | 112 lb | 2240 lb. |
AVON, the name of several rivers in England and elsewhere. The word is Celtic, appearing in Welsh (very frequently) as afon, in Manx as aon, and in Gaelic as abhuinn (pronounced avain), and is radically identical with the Sanskrit ap, water, and the Lat. aqua and amnis. The root appears more or less disguised in a vast number of river names all over the Celtic area in Europe. Thus, besides such forms as Evan, Aune, Anne, Ive, Auney, Inney, &c., in the British Islands, Aff, Aven, Avon, Aune appear in Brittany and elsewhere in France, Avenza and Avens in Italy, Avia in Portugal, and Avono in Spain; while the terminal syllable of a large proportion of the Latinized names of French rivers, such as the Sequana, the Matrona and the Garumna, seems originally to have been the same word. The names Punjab, Doab, &c., show the root in a clearer shape.
In England the following are the principal rivers of this name.
1. The East or Hampshire Avon rises in Wiltshire south of Marlborough, and watering the Vale of Pewsey collects feeders from the high downs between Marlborough and Devizes. Breaching the high ground of Salisbury Plain, it passes Amesbury, and following a very sinuous course reaches Salisbury. Here it receives on the east bank the waters of the Bourne, and on the west those of the Wylye. With a more direct course, and in a widening, fertile valley it continues past Downton, Fordingbridge and Ringwood, skirting the New Forest on the west, to Christchurch, where it receives the Stour from the west, and 2½ m. lower enters the English Channel through the broad but narrow-mouthed Christchurch harbour. The length, excluding lesser sinuosities, is about 60 m., Salisbury being 35 m. above the mouth. The total fall is rather over 500 ft., and that from Salisbury about 140 ft. The river is of no commercial value for navigation. It abounds in loach, and there are valuable salmon fisheries. The drainage area is 1132 sq. m.
2. The Lower or Bristol Avon rises on the eastern slope of the Cotteswold Hills in Gloucestershire, collecting the waters of several streams south of Tetbury and east of Malmesbury. It flows east and south in a wide curve, through a broad upper valley past Chippenham and Melksham, after which it turns abruptly west to Bradford-on-Avon, receives the waters of the Frome from the south, and enters the beautiful narrow valley in which lie Bath and Bristol. Below Bristol the valley becomes the Clifton Gorge, famous for its wooded cliffs and for the Clifton (q.v.) suspension bridge which bestrides it. The cliffs and woods have been so far disfigured by quarries that public feeling was aroused, and in 1904 an "Avon Gorge Committee" was appointed to report to the corporation of Bristol on the possibility of preserving the beauties of the locality. The Avon finally enters the estuary of the Severn at Avonmouth, though it can hardly be reckoned as a tributary of that river. From Bristol downward the river is one of the most important commercial waterways in England, as giving access to that great port. The Kennet and Avon Canal, between Reading and the Avon, follows the river closely from Bradford down to Bath, where it enters it by a descent of seven locks. The length of the river, excluding minor sinuosities, is about 75 m., the distance from Bradford to Bath being 10 m., thence to Bristol 12 m., and thence to the mouth 8 m. The total fall is between 500 and 600 ft., but it is only 235 ft. from Malmesbury. The drainage area is 891 sq. miles.
3. The Upper Avon, also called the Warwickshire, and sometimes the "Shakespeare" Avon from its associations with the poet's town of Stratford on its banks, is an eastern tributary of the Severn. It rises near Naseby in Northamptonshire, and, with a course of about 100 m. joins the Severn immediately below Tewkesbury in Gloucestershire. Its early course is south-westerly to Rugby, thereafter it runs west and south-west to Warwick, receiving the Leam on the east. Its general direction thereafter remains south-westerly, and it flows past Stratford-on-Avon, receives the Stour on the south and the Arrow on the north and thence past Evesham and Pershore to Tewkesbury. The valley is always broad, and especially from Warwick downward, through the Vale of Evesham, the scenery is very beautiful, the rich valley being flanked by the bold Cotteswold Hills on