MAU 





MAC 



other being made to touch the other ex- 

 tremity, is applied to the knob of the in- 

 ner coating, to make the discharge. The 

 animal or substance thus forming a part 

 of the circuit, receives the whole shock. 

 The strong shock of a battery will melt 

 wire of the seventieth of an inch in dia- 

 meter, and wires of less diameters are 

 frequently blown away and dispersed; 

 and the eflect is the same with equal 

 quantities of electricity, whether the in- 

 tensity be greater or less, within certain 

 extended limits. Gunpowder may be 

 fired by a charge of three square feet : 

 the method is, t^o put it into a quill, and 

 thrust a wire into each end, so as not to 

 meet, and then make these wires a part 

 of the circuit. A less charge will serve, 

 if iron filings be mixed with the gunpow- 

 der. Alcohol, ether, or a mixture of com- 

 mon air and hydrogen, may also be fired 

 by the same means, or even by the spark 

 from the conductor. 



If the ball of a thermometer be placed 

 in a strong current of electricity, the 

 mercury or spirit will rise many de- 

 grees. 



If a thin bottle be exhausted of air by 

 means of the air-pump, it will receive a 

 considerable charge by applying its bot- 

 tom to the electrified prime conductor, 

 during which time the electric matter 

 will pass through the vacuum between 

 the hand and the inner surface of that 

 part of the glass which is nearest the 

 prime conductor. This appearance is ex- 

 ceedingly beautiful in the dark, especially 

 if the bottle be of a considerable length. 

 It exactly resembles those lights which 

 appear in the northern sky, and are call- 

 ed streamers, or the aurora borealis. If 

 one hand be applied to the part of the 

 bottle which was applied to the conduc- 

 tor, while the other remains at the neck, 

 the shock will be felt, at which instant 

 the natural state of the inner surface is 

 restored by a flash, which is seen per- 

 vading the vacuum between the two 

 hands. 



MACHINERY, in epic and dramatic 

 poetry, is when the poet introduces the 

 use of machines, or brings some super- 

 natural being upon the stage, in order to 

 solve some difficulty, or to perform some 

 exploit out of the reach of human power. 

 The ancient dramatic poets never made 

 use of machines, unless where the re was 

 an absolute necessity for so doing; whence 

 the precept of Horace, 



" Ncc Deus intersit, nisi dignus vindice 

 noJas incident. 



It is quite otherwise with epic poets, 

 who introduce machines in every part ot 

 their poem ; so that nothing is done with- 

 out th? intervention of the gods. In Mil- 

 ton's Paradise Lost, by far the greater 

 part of the actors are supernatural per- 

 sonages : Homer and Virgil do nothing 

 without them ; and in Voltaire's Henri- 

 ade, the poet has made excellent use of 

 Saint Louis. 



MACKREL, in ichthyology. See ICOM- 

 BER. 



MACLAURIN (COLIN,) in biography, 

 a most eminent mathematician and phi- 

 losopher, was the son of a clergyman, and 

 born at Kilmoddan in Scotland, in the 

 )ear 1698. He was sent to the university 

 of Glasgow in 17^9 ; where he continued 

 five years, and applied to his studies in a 

 very intense manner, and particularly to 

 the mathematics. His great genius for 

 mathematical learning discovered itself 

 so early as twelve years of age ; when, 

 having accidentally met with a copy of 

 * Euclid's Elements" in a friend's cham- 

 ber, he became in a few days master ot" 

 the first six books without any assistance; 

 and, it is certain, that in liis sixteenth 

 year he had invented many of the propo- 

 sitions which were afterwards published 

 as part of his work, entitled, " Geome- 

 trix Organica." In his fifteenth year he 

 took the degree of Master of Arts ; on 

 which occasion he composed, and pub- 

 licly defended, a thesis on the power of 

 gravity, with great applause. After this 

 he quitted the university, and retired to 

 a country seat of his uncle, who had the 

 care of his education ; his parents being- 

 dead some time. Here he spent two or 

 three years in pursuing his favourite stu- 

 dies ; but in 1717, at nineteen years of age 

 only, he offered himself a candidate for 

 the professorship of mathematics in the 

 Marischal College of Aberdeen, and ob- 

 tained it after a ten day's trial, against a 

 very able competitor. 



In 1719, Mr. Maclaurin visited London, 

 where he left his " Geometria Organica' 3 

 to print, and where he became acquainted 

 with Dr. Hoadley, then bishop of Banker, 

 Dr. Clarke, Sir Isaac Newton, and olhci 

 eminent men . at which time also he was 

 admitted a member of the Royal Society ; 

 and in another journey in 1721, he con- 

 tracted an intimacy with Martin Folkes, 

 Esq. the president of it, which continued 

 during his whole life. 



In 1722, Lord Polwortli, plenipoten- 

 tiary of the King of Great Britain at the 

 congress of Cambray, engaged Maclaurin 

 to go as a tutor and companion to his 



