Xi'lUL POINTS AND LINKS. 



NOMINALISTS. 



! - 



fixed object, or, if at may part of the surface, one of the fingers of the 

 head m\\ be pressed gently upon that part. The plate being in a 

 horizontal potiUon.it must be covered with a layer of fine dust such 

 as lyeopodjum; and it may be put in a state of vibration l>y drawing 

 a violin-bow across its edge : the dust will then arrange itself in figures 

 which will vary with the form of the plate, the place at which the bow 

 is applied, an<l that at which the plate is held. If, for example, a 

 square plate be held at its centre, and the bow be applied near one of 

 the angles, the dust will arrange itself in lines so as to divide the plate 

 into four equal squares (So. I). It the plate be held an before, and 



SV I. 



!fo. J. 



No. 3. 



No. 4. 



the bow be applied at the middle of one of the sides, the vibrations 

 will be such as to make the dust lie in the direction of the two iago- 

 nals (No. 2). Again, if the plate be held at A (No. 3) and the bow be 

 applied at B, the dust will assume the positions of three lines parallel 

 to one another : and if the plate be held at a point nearer the edge, the 

 lines will become curves, as in No. 4. 



If a circular plate, held at the centre, be pressed against a fixed 

 object at any point on its circumference, and the bow be applied at 

 45" from that point, the lines trill take the positions of two diameters 

 at right angles to one another, one of them passing through the point 

 at which the circumference touches the object. A greater number of 

 radiating lines than four will be produced if the bow be drawn 

 more rapidly and with less pressure against the edge of the plate than 

 in the former case. If the centre of the circular plate be free, various 

 curve lines will be assumed by the dust, according to the position of 



No. S. 



No. 6. 



No. 7. 



No. 8. 



the point which is held ; and one of them is represented in No. 5. The 

 figures represented in Nos. 6, 7, and 8, are selected from the great 

 number which Chladni has obtained with glass plates of a circular, a 

 polygonal, and a triangular form. Professor Wheatstone has calculated 

 a large number of these acoustic figures by the principle of the super- 

 position of small motions. ( 1'hil. Trans.) Professor Faraday also 

 describes (Phil. Trans., 1831) a number of interesting experiments on 

 the subject. 



Beautiful acoustic figures may also be obtained on the surface of 

 mercury, water, spirit, &c., contained in a glass goblet, by drawing a 

 violin-bow against its edge. This part of the subject is fully and carefully 

 investigated in Mr. Tomlinson's ' Student's Manual of Natural Philo- 

 sophy,' (1838). M. Felix Savart has observed, that if a rectangular plate 

 of glass about 27 inches long, ] inch broad, and ,' inch thick, b8 held 

 horizontally between a finger and thumb at the middle of its opposite 

 edges, and it be put in a state of longitudinal vibration, either by rub- 

 bing its under side, near one of the ends, with a wet cloth, or by striking 

 it gi-ntly at one end, the dust on the upper surface will arrange itself in 

 line* perpendicular to the length of the rod. It is remarkable, that if 

 the plate be turned with its upper face downwards, being held as before, 

 and vibrations be produced in like manner, the places of the nodal 

 lines will be opposite to the middles of the intervals between the lines 

 observed in the other position of the plate a circumstance which 

 proves that the motions of the particles in one-half of the thickness of 

 the lamina of glass are directly contrary to those iu the other half. A 

 like effect has been observed when cylindrical rods of glass have been 

 made to vibrate longitudinally ; the lines of nodes then assuming a 

 spiral form about the cylinder, and the curves consisting of portions 

 which run alternately in contrary directions : the points of greatest 

 and least inclination to the axis uf the cylinder are at U0 from each 

 other with respect to a line drawn on the surface parallel to the axis, 

 and the effect is such as would arise if the cylinder were divided longi- 

 tudinally into four quadranta) portion*, having opposite qualities. The 

 place* of the nodes on that part of the ml which was uppermost were 

 found, the rod being held in a horizontal position, by annular pieces of 

 paper loosely encircling it. 



In 1822. ft. Savart read to the Academic des Sciences at Paris, an 

 account of some curious experiment* in which acoustic figures were 

 produced in consequence of vibrations communicated through the air 

 to elastic membranes. (' Brewster's Edinburgh Journal of Science,' 

 vol. ii , p. 2W.) A sheet of thin paper was slightly stretched over a 

 glass vessel four or five inches in diameter, and on it was strewed light 

 dost. A thin circular plate of glass, in a state of vibration, was then 

 brought within a f-w inches of th'; piper, when the vibrations were 

 communicated to the latter, and, the paper being of uniform thickness 



and well stretched, the dust assumed figures which were p 

 regular. M. Savart, having rendered the glass plate immoveable at 

 opposite points on its circumference by holding it there between the 

 thumb nnd a finger of each hiiml, placed the tip of another finger at a 

 point on the surface, at a distance from the centre equal to about one- 

 fifth of the diameter, and caused the plate to vibrate by drawing a 

 violin-bow across its circumference. In these circumstances, on pre- 

 senting the plate to the stretched paper, the following appearances 

 were observed. The nodal figures on square paper were analogous to 

 those formed on a square plate of glass or metal, and on circular plates 

 their general character was circular. The circular lines were some- 

 times cut by diametrical lines which formed nodal points, or stars, 

 and the number of these increased with the acuteness of the sound 

 produced^ the bow. When the plate of glass was parallel to the 

 paper, the nodal lines were similar on both, as when two plates were 

 connected with each other, by a rod fixed perpendicularly between 

 them. When the plane of the glass plate was hold vertically, the 

 nodal lines on the paper became parallel to one another ; am! the 

 figures on the paper changed as the glass plate was made to decline 

 from the vertical position. 



Some curious acoustic figures have been produced by M. Lissajoux 

 by attaching a mirror to one of the prongs of a tuning fork, and allow- 

 ing a ray of light to fall somewhat obliquely on the mirror. It is 

 evident that under such circumstances the direction of the reflected 

 ray will change with every vibration of the fork, and on allowing this 

 reflected ray to fall on the screen, the vibrations of the fork become 

 visible in the rapid motions of a point of light on the screen. In this 

 way M. Lissajoux has rendered the vibratory ni.ivini.iit ol 

 bodies visible and has made evident the optical composition of vibra- 

 tory motions which take place in the same direction : he has also been 

 able to compound two vibratory motions at right angles to each other ; 

 to show the accordance of two diapasons separated by a n 

 interval, and to give the means of fixing on a constant or invari.iMi- 

 fundamental sound. The only fault of this highly suggestive method 

 is that it does not leave a permanent trace of its indications. 



NODE. The points of a planet's or comet's orbit in which it cuts 

 the ecliptic, and the points in which the orbit of a satellite cuts that of 

 its primary, are called the nodes of such planet, comet, or satellite. 

 Generally, the point in which one orbit cuts a second is called the nodi' 

 of the first n/mn the second. 



NOLLE PROSEQUI is a phrase used in proceedings at law to 

 denote the withdrawal of the plaintiff from the further prosecution of 

 his suit, and is derived from the words used in the formal entry of 

 such withdrawal on the record, in which the party "acknowledges that 

 he will not further prosecute" (fatetur se ulterius nulle proiequi), the 

 consequence of which is that the defendant is entitled to his costs, 

 under stat. 8 Eliz., c. 2, s. 2. In equity, the complainant can at any time 

 discontinue his suit upon an application to the court, and paying the 

 costs of the defendant, as he likewise may do at law. In criminal pro- 

 secutions by indictment, which are in the name of the drown, t 

 originated by private persons, a nolle prosequi may be enter. ,i 

 attorney-general, but not without his concurrence, although the pro- 

 secutor desires it. It is very unusual however for the ati 

 general to enter a nolle prosequi upon an indictment, oxe.ept upon the 

 application of the prosecutor. Lord Holt says, " the practice began in 

 the reign of Charles II., and that in all Charles I.'s time tin ]< 

 precedent of a nolle prosequi upon an indictment." (ii M"<f, /.'/)., 262.) 

 There can be no doubt of the power of the attorney-general to put an 

 end to criminal information* filed er nffifio by him ; and in the case of 

 informations in the Court of Queen's Bench, a nolle prosequi in 

 entered by the master of the crown-office upon the application of the 

 prosecutor and with the leave of the court. The effect of a nolle pro- 

 sequi in criminal cases is to discharge the defendant for the time, 

 but it does not operate as an acquittal; so that he may be in 

 again, and it is said that even upon the same indictment fresh process 

 may be awarded. 



NOMENCLATURE, CHEMICAL. [CHKMTCAL NOMENCLATI-RE.] 



NOMINALISTS, a sect of the scholastic philosophers. BO nam 

 account of the particular tenet by which they were distinguished, ami 

 in opposition to the Realists, another scholastic sect. In oroVr t.. 

 understand the principal point of difference between these | 

 which gave rise to long-continued and acrimonious disputation, it is 

 necessary to advert to the doctrines of the ancient philosophy cv 

 ing ideas or universal*. According to Plato, who appears to nave been 

 indebted for his opinion to the Pythagorean school, universal*, or, as 

 he called them, ideas, by which are to bn understood such things as we 

 express by general terms, have, apart from the mere conception of 

 them by the understanding, an actual and eternal existence in th" 

 Divine Mind ; and are the patterns or models according to which the 

 individuals of every species are formed, and by which the constitution 

 of each individual is determined. The separate existence of these 

 essences was denied by Aristotle, who taught that forms which word 

 as employed by him has the same meaning with the ideas of Plato 

 were eternally united to matter ; that unconnected with it i 

 existence, and that they arc inherent in their objects. Zenoancl the Stoics 

 generally ridiculed the belief in such universal natures altogether ; ami 

 held that the forms of the Stagyrite and the ideas of In 

 were nothing if distinguished from the notions of them in the mind 



