NOR 



NOT 



if their whole surface he excited, and 

 they are then touched by some conductor 

 connected with the ground, they part 

 with their free electricity only at the 

 point of contact. Their characteristic is, 

 that they retain free electricity for a 

 length of time, and that they check its 

 motion. 



NON-ELECTRICS. It was formerly 

 thought that none but the non-conductors 

 could be electrically excited, and that no 

 other bodies possessed electricity ; hence 

 the name of electrics was given to the 

 former, and that of non-electrics to the 

 latter class of substances. 



NONAGE'SIMAL DEGREE. The 

 highest point of the ecliptic above the 

 horizon. Every point, therefore, of the 

 ecliptic is the nonagesimal degree in 

 succession. 



NO'NAGON {novem, nine, YMvt'a, an 

 angle). In Geometry, a plane figure 

 having nine angles and consequently 

 nine sides. See Enneagon, which is a 

 classical term, the other being barbarous. 



NO'NIUS. A former designation of 

 the Vernier, from its having been sup- 

 posed that this instrument was merely 

 an improvement of the method of sub- 

 division adopted by Nunnez, a Portu- 

 guese. See Vernier. 



NO'NTRONITE. Silicate of iron ; a 

 mineral occurring in small nodules in an 

 ore of manganese, and found in the de- 

 partment of Dordogne in France, in the 

 arrondissement of Nontron. 



NOON, REAL and APPARENT. In 

 Astronomy, the word apparent is used 

 not as opposed to real, but as coinciding 

 with it, and opposed to mean. Thus ap- 

 parent noon means real or true noon, 

 when the true sun, the sun which 

 appears, is on the meridian, as opposed 

 to mean noon, when the mean sun, the 

 average fiction of astronomers, which 

 does not appear at all, is on the meri- 

 dian. See Mean Noon. 



NOOTH'S APPARATUS. An appa- 

 ratus invented by Nooth for making a 

 solution of carbonic acid gas. 



NORFOLK CRAG. A tertiary form- 

 ation resting on London clay or chalk. 

 It is included by a line drawn from 

 Cromer to Wayburn, and thence southerly 

 about eighteen miles towards Norwich. 



NORMA. The Rule ; a constellation 

 situated between Scorpio and Lupus. 



NORMAL (norma, a rule). From its 



original meaning of a rule, as used by 



builders, this term was used to signify a 



perpendicular ; but it is generally em- 



235 



ployed to denote the perpendicular to a 

 curve at some particular point, at which 

 point the normal is also perpendicular to 

 a tangent. 



NORMAL GROUPS [norma, a rule 

 or pattern). Groups of certain rocks 

 taken as a rule or standard. 



NORTH-WEST CURRENT. A 

 branch of the great Equatorial Current^ 

 which separates from the equatorial at 

 22° w. long., takes a north-western direc- 

 tion, and is eventually lost in the drift 

 current, to which it seems to give a 

 north-westerly direction, which is ob- 

 servable from 35° w. long, to Trinidad. 



NORTHERN LIGHTS. Luminous 

 appearances in the horizon, less trans- 

 ient in their duration than the light- 

 ning, of frequent occurrence in the higher 

 latitudes, more rare in the temperate 

 zones, and scarcely ever seen within the 

 tropics. In the northern hemisphere the 

 illuminated part surrounds the north 

 pole, in the opposite hemisphere the 

 south pole ; hence the respective names 

 of horealis and australis applied to the 

 aurora. 



NOTACA'NTHA (i/Sror, the back, 

 aKav9a, a spine). A section of Dipterous 

 insects, in which the upper part of the 

 thorax or scutellum is armed with spines. 



NOTATION {noto, to mark). The 

 act or practice of recording any thing by 

 marks, as by figures or letters. \. Ma- 

 thematical notation comprises symbols 

 of number ; symbols of quantity, which 

 are usually letters ; and symbols of ope- 

 ration, as employed in algebra. 2. Nota- 

 tion in Music signifies the method 

 whereby the pitch or tune, and the dura- 

 tion of musical sounds are represented, 

 and by which definite periods of silence, 

 called rests, are marked. It is to music, 

 what letters and punctuation are to lan- 

 guage. 



NOTHOSAU'RUS {voOo^, spurious, 

 uavpny a lizard). A spurious kind of 

 saurian, found in the shelly limestone 

 occurring in the middle of the sandy beds 

 of the New Red Sandstone Formation. 



NOTIONAL and RELATIONAL. 

 By these terms, Dr. Becker distinguishes 

 all the words of language into two classes, 

 notional words being those which ex- 

 press notions, or objects of the under- 

 standing, as verbs and nouns ; while 

 relational words are either mere termina- 

 tions of notional words, expressing a 

 relation between different objects, or sepa- 

 rate words expressing relation, as pre- 

 positions. The former class of words 



