BUR 



BUR 



and rose again when the matrass was re- 

 moved. When nitric acid was poured 

 upon the snow (which increased the 

 cold) the thermometer sunk 5 or 6 

 lower. Here cold seems to have been 

 emitted by the snow, and reflected by 

 the mirrors to the thermometer, which 

 it is thought could not happen unless 

 cold were a substance. It has been found, 

 that upon an admixture of equal quanti- 

 ties of snow, which is always at 32, and 

 of water heated to 172, the result is, that 

 the compound only retains the lowest 

 heat of 32, so that 140 of heat or calo- 

 ric disappears. Much has been said re- 

 specting the point or degree at which the 

 thermometer should indicate the pre- 

 sence of heat. The experiments of Dr. 

 Crawford seem to place it at 1268 below 

 the present ; Mr. Kirwan places it at 

 1048; Messrs. Lavoisier and La Place at 

 2736 ; and by a mixture of four parts of 

 sulphuric acid with three pints of water, 

 it seems that it should be placed at 5803 

 below 0. Experiments of this kind may 

 be made ad infinttum, and in time it may 

 possibly be ascertained that cold is a real 

 substance ; but for the purpose of get- 

 ting an answer to the present question, 

 we will accommodate the scale of Fah- 

 renheit, by adding 108 thereto, so as to 

 make the correspond with the caloric 

 imbibed by snow or ice before it can 

 melt. 



The superficies of spherical bodies are 

 to each other as the squares of their re- 

 spective diameters. The diameter of the 

 moon is considered to be 2180 miles, and 

 its mean distance from the earth 240,000 ; 

 from which it follows, on the supposition 

 that all the solar rays received by the 

 moon were reflected back, and that the 

 earth was absolutely without heat, that 

 the effect of this reflection would be 

 found to be .00367 of a degree (for 

 240,000X2": 178 :: 2180 : .00367); which 

 multiplied into 1056.25, and this sum in- 

 creased four times for the increased power 

 of the second lens, would give 15.51234 

 as the heat of the focus; 98.28766 be- 

 low the present 0, or 124.28766 below 

 the freezing point. This dissertation is 

 interesting in another point of view, for 

 this calculation ascertains that the light 

 afforded by the moon, when compared 

 with that by the sun, abstracting all im- 

 pediments in both cases, is only as 1 to 

 48480. 



A subscription was proposed for raising 

 the sum of 700 guineas towards indemni- 

 fying the charges of the inventor, and re- 

 taining the very curious and useful ma- 

 chine above described in our own coun- 



try ; but from the failure of the subscrip- 

 tion, and some other concurring circum- 

 stances, Mr. Parker was induced to dis- 

 pose of it to Capt. Mackintosh, \vlio ac- 

 companied Lord Macartney in the embas- 

 sy to China; and it was left, much to the 

 regret of philosophers in Europe, at Pe- 

 kin; where it remains in the hands of 

 persons, who most probably know neither 

 its value nor use. 



BtrnNiire-mOTwitam*, the same with vol- 

 canoes. See VOLCANO. 



BURNISHER, a round polished piece 

 of steel, serving to smooth and give a lus- 

 tre to metals. 



Of these there are different kinds, of 

 different figures, straight, crooked, Sec. 

 Half burnishers are used to solder silver, 

 as well as to give a lustre. 



BURNISHING, the art of smoothingor 

 polishing a metalline body by a brisk rub- 

 bing of it with a burnisher. 



Book -binders burnish the edges of 

 their books by rubbing them with a dog's 

 tooth. Gold and silver are burnished by 

 rubbing them with a wolf's tooth, or by 

 the bloody stone, or by tripoli, a piece of 

 white wood, emery, and the like. Dest 

 are said to burnish their heads by rub- 

 bing off a downy white skin from their 

 horns against a tree. 



BURR pump, or BILDGK pump, differs 

 from the common pump in having a staff 

 6, 7, or 8 feet long, with a bar of wood, 

 whereto the leather is nailed, and this 

 serves instead of a box. So two men. 

 standing over the pump thrust down this 

 staff, to the middle whereof is fastened a 

 rope for 6, 8, or 10 to hale by, thus pull- 

 ing it up and down. 



BURSARIA, in natural history, a genus 

 of worms of the order Infusoria. Worm 

 very simple, membranaceous, hollow- 

 There are three species, viz. the trunca- 

 tella, hirundinella, and duplella, found in 

 marshy water : the first has a white body, 

 oval, with a large hollow descending to 

 the base, with sometimes four or five 

 eggs at the bottom : the second is a pel- 

 lucid hollow membrane, moving forwards 

 like a bird in flight ; the third is found 

 among duck-weed, without visible in- 

 testines. 



BURSARS, in the Scotch universities, 

 are youths chosen as exhibitioners, and 

 maintained for the space of four years at 

 the rate of 100^. per ami. Scots. 



BURSE, in a commercial sense, a place 

 for merchants to meet in and negociate 

 their business publicly, with us called ex- 

 change. 



BURSERA, in botany, so called in ho- 

 nour of Joachim Burser, a genus of the 



