AUR 



AUR 



imperial chamber of Spire is perpetual, 

 representing not only the deceased em- 

 peror, but the whole Germanic body, 

 which is reputed never to die. 



AVOIRDUPOIS, or AVKRDUPOIS -weight, 

 a sort of weight used in England, the 

 pound whereof is made up of sixteen 

 ounces. 



This is the weight for the larger and 

 coarser commodities, such as groceries, 

 cheese, wool, lead, &c. Bakers, who live 

 not in corporation-towns, are to make 

 their bread by avoirdupois weight ; those 

 in corporations, by troy weight. Apothe- 

 caries buy by avoirdupois weight, but sell 

 by troy. The avoirdupois ounce is less 

 than the troy ounce, in the proportion 

 of 700 to 768 ; but the avoirdupois pound 

 is greater than the troy pound, in the 

 proportion of 700 to 576, or as 17 to 14 

 nearly : for 



1 lb. avoirdupois = 7000 grains troy. 

 1 Ib.troy . . = 5760 . . do. 

 1 or. avoirdupois = 437^ . . do. 

 loz.troy . . = 480 . . do. 



AVO WEE, one who has a right to pre- 

 sent to a benefice. See ADVOWSOX. 



AURELIA, in natural history, a term 

 formerly employed by naturalists to ex- 

 press that intermediate state, in which all 

 lepidopterous, and most other insects, 

 remain for some time, between the cater- 

 pillar form and the period in which they 

 are furnished with wings, with antennae, 

 and other organs appertaining to the per- 

 fect insect. Aurelia and crysalis are 

 synonymous words, both alluding to the 

 golden splendour of the case in which the 

 creature, during that state, is contained. 

 This brilliant appearance seems to be 

 confined to the Papilio tribe, so that the 

 terms aurelia and crysalis are altogether 

 inapplicable, in a general manner, to in- 

 sects in that state. These terms are now 

 discarded in favour of the more expres- 

 sive one pupa, which Linnreushas adopted 

 in their stead ; a term which implies that 

 the insect, like an infant, remains in its 

 swaddling clothes. 



AURICLE, in anatomy, that part of the 

 ear which is prominent from the head, 

 called by many authors auris externa. 



AURICLES of the heart. These are a kind 

 of appendages of the heart at its base, and 

 are distinguished by the names of the 

 right and left. The right auricle is much 

 larger than the left, and this is placed in 

 the hinder, that in the anterior part. They 

 are intended as diverticula for the blood, 

 during the systole. Their substance is 

 muscular, being composed of strong 



fibres, and their motion is not synchro^ 

 nous, but achronous, with that of the heart. 

 See AXATOMY, 



AURICULAR medicines, such as are 

 used in the cure of distempers in the ear. 



AURIGA, the Waggoner, in astronomy, 

 a constellation of the northern hemis- 

 phere, consisting of 23 stars, according to 

 Tycho, 40 according to Hevelius, and 66 

 in the Britannic catalogue. This constel- 

 lation is represented by the figure of an 

 old man, in a posture somewhat like sit- 

 ting, with a goat and her kids in his left 

 hand, and a bridle in his right. 



AURORA borealis, or AURORA septen- 

 trionalis, in physiology, the northern dawn 

 or light, sometimes called streamers, is 

 an extraordinary meteor, or luminous ap- 

 pearance, shewing itself in the night-time 

 in the northern part of the heavens ; and 

 most usually in frosty weather. It is usual- 

 ly of a reddish colour, inclining to yellow, 

 and sends out frequent corruscations of 

 pale light, which seem to rise from the 

 horizon in a pyramidal undulating form, 

 and shoot with great velocity up to the 

 zenith. The aurora borealis appears fre- 

 quently in form of an arch, chiefly in the 

 spring and autumn after a dry year. The 

 arch is partly bright, partly dark, but ge- 

 nerally transparent ; and the matter of 

 which it consists is also found to have no 

 effect on the rays of light which pass 

 through it. Dr. Hamilton observes, that 

 he could plainly discern the smallest 

 speck in the Pleiades, through the densi- 

 ty of those clouds which formed the au- 

 rora borealis in 1763, without the least 

 diminution of its splendour, or increase of 

 twinkling. 



This kind of meteor, which is more un- 

 common as we approach towards the 

 equator, is almost constant during the 

 long winter, and appears with the great- 

 est lustre in the polar regions. In the 

 Shetland isles, the " merry dancers," as 

 the northern lights are there called, are 

 the constant attendants of clear evenings, 

 and afford great relief amidst the gloom 

 of the long winter nights. They common- 

 ly appear at twilight near .the horizon, 

 of a dun colour, approaching to yellow ; 

 they sometimes continue in that state for 

 several hours, without any perceptible 

 motion ; and afterwards they break out 

 into streams of stronger light, spreading 

 into columns, and altering slowly into 

 10,000 different shapes, and varying their 

 colours from all the tints of yellow to the 

 most obscure russet. They often cover 

 the whole hemisphere, and then exhibit 

 the most brilliant appearance. Their 

 motions at this time are most amazingly 



