BOLD. 



MOTION. 



fork* are said to take fifteen or twenty yean 



larger and mow elabo. 



in copying. The sole advantage in any degree proportionate to the 

 eost Mfnv<i"g it, U the extreme durability of the work when ouoe 

 XKicmplisnnd, aa ita colours can hardly be changed by any length of 

 time ; nor i it liable to decay or injury, except what may happen to 

 the structure in which it U fixed. The mosaic* in St. Peter's, which 

 are masterpiece* of their kind, may be expected to laat as long as the 

 building itaelf stands. When Sir Christopher Wren designed St. Paul's 

 it waa his earnest wish to hare the cupola decorated with mosaics, like 

 the cupola of St. Peter's, and he had actually entered into negotiations 

 with some Italian musaicisti for their execution, but the authorities 

 would not give their sanction. Quite recently proposals have been 

 issued by the present dean and chapter for carrying out Wren's 

 intentions, accordinn to a plan drawn up by Mr. Penroae, the present 

 architect to the cathedral Many teaselated pavements of good design 

 and excellent workmanship have been laid down in this country within 

 the last few years. 



The modern Italian musaicisti have reached almost the perfection of 

 t^hni^l md manipulative dexterity. Their mode of working differs, 

 however, little in principle from that of the mediaeval workers in 

 mosaic. They employ for the ground of their work a plate of metal 

 or a slab of travertine, the size of the picture, and this is surrounded 

 by an iron frame. In this bed is spread a cement or stucco, com- 

 posed of mastic, powdered travertine, and carbonate of lime, mixed 

 with linseed oil, so as to form a paste. The tessera;, or smalti, of 

 which the picture is composed, are imbedded in the cement, winch 

 is only laid as far as the musaicisti are ready to proceed at one 

 time, as it remains but a short period in a fit state for working 

 on, and eventually hardens to the consistency of stone. When the 

 whole picture is completed the surface is rubbed smooth to remove 

 all inequalities, and brought to a polish, or left dull, according to 

 the position the picture is intended permanently to occupy. The 

 smalti are of opaque glass, coloured with metallic oxides and pre- 

 pared in a peculiar manner. They vary in size from an inch square to 

 a pin's head. The mediaeval mode of working and materials, will 

 be found described in Mrs. Merrifield's ' Ancient Practice of Painting,' 

 v. L, p. lii. tc. 



Something akin to mosaic or coloured inlaid-work waa occasionally 

 employed in Italy during the middle ages for external decoration 

 alao ; as an instance of which the facade of the Duomo at Pisa may be 

 mentioned, where, though the pattern is chiefly in black and white, 

 brilliant reds and blues are intermixed at intervals, a species of external 

 decoration supposed by some to have been derived from the practice of 

 polyduvmy among the Greeks. [POLTCHROMY.] This is much the 

 character of the Oriental mosaic, of which the mosques of Cairo and 

 Damascus afford very beautiful examples. On the resemblance between 

 Oriental and Byzantine mosaic work, and the characteristics of the 

 former, see ' Heesemer's Arabische uud Alt-Italienische Bau-Ver- 

 zierungen.' 



Pietra Dura, or Florentine work, is a kind of mosaic, in which l>y 

 pieces of coloured stones and marbles, figures or patterns are formed 

 on marble slabs for tables and decorative purposes. An imitation of it 

 U manufactured to some extent with Derbyshire marbles at Matlock, 

 Derby, and Buxton. There U a fine sort of Florentine work, called in 

 Italy, Pietra Coinmease, which is executed with agates, jasper, and 

 other precious stones, cut into various shapes and sizes; it is an elegant 

 but very costly style of ornamentation. 



What was called Tartia work, or Tan'utttura, was a kind of mosaic in 

 wood, by which landscapes and patterns were inlaid in walnut panels, 

 by means of small pieces of wood of various shades and colours. A 

 very humble imitation of it is the inlaid toy-work known as Tunbridge- 

 ware. 



(Furietti, Th ilutivi* Roma (1752) ; Ciampini, Vetera Monimtnta ; 

 Mazois, L-t Ruina de Ponpti ; Donaldson, Pompeii ; Laborde, Mot. 

 fffialica; Muller, llandbach der A rchaotoijie ; and Archnnl. der Alien 

 Kxntt; D'Agincourt, Hat. de FArt, tab. 13, 4c. ; Merrifield, Ancient 

 Practice of Painting, voL i. ; M. D. Wyatt, Specimen! of the Geometrical 

 MoMicof the Middle Aga ; Secchi, Munaico Antoniano dacritto e Illui- 

 trato ; Kreutz, La Jlaiilica di San Marco in Venezia, etpoita ne mvi 

 tfatfid; Oruner, The Sfotaia of the Cupola, in the ' Cafpella C'Ai;/i<i>u ' 

 of Sta. Maria del Popvlo in Some, designed by Kaffuello Sanzio 

 .11 rUno.) 



MOSAIC GOLD. [Ti*, KnJphide of.] 



MOSQUE (from the Arabic ilatchind or tfedtchcd, and inter 

 mediately the Spanish and Portuguese tfc;>/itita and Mcuautta), a 

 Mohammedan place of worship, the distinctive marks of which are 

 generally cupolas and minareta. [SAHACKMC ARCIIITKCTUKK.] Int. i 

 nally the mosques exhibit nothing remarkable as to plan or accommo- 

 dation, forming merely a single large hall or apartment, without any 

 aaU or other fittinga-up, and with no other decoration than tint l 

 pavements and carpets, or arabesques and mosaics on the walls. In 

 regard to these Utter, some of the mosques at Cairo are highly 

 embellished. Although more famed than any other, the mosque of 

 Santa Sophia at Constantinople exhibits nothing of Mohammedan or 

 Arabian architecture, but was originally built as a church, and is in 

 the liyiantine style. (BYZAXTIMK AncaiTKCTURB.] The mosque of 

 the Sultan Achmet, called the At-Meidan, at Constantinople, though 

 of much later date, shows the influence of the Byzantine model 



we give an engraving of it as an excellent example of a Turkish 

 mosque. 



MOTET (ifottetlo, Ital.), in Music, a vocal composition set to sacred 

 words, and used in the Roman Catholic church. The word was syno- 

 nymous with anthem, when first introduced, and signified a superior 

 kind of hymn, accompanied only by the organ. [ANTHKM.] Latterly 

 however the Motet has lost much of its primitive solemnity, having 

 been, for considerably more than half a century, written with full and 

 florid orchestral accompaniments, and thus, like the Mass, is deprived 

 of no small portion of its devotional character. Many attempts have 

 been made to discover whence the word is derived, but without any 

 satisfactory result. 



MOTHKR-LIQUOR. [MOTHER- WATER.] 



MOTHER- WATER. When any saline solution has been evaporated 

 so as to deposit crystals on cooling, the remaining solution is termed 

 the mother-water, or mother-liquor, or sometimes merely the mothers. 



MOTION is change of place ; there has been motion when ;> 

 at one time, occupies a part of space different from that in which it 

 waa at a preceding time. The only additional necessary conception is 

 continuity of change : every point which has moved from one point of 

 space to another must have passed over every part of some line, 

 straight or not straight, drawn from one point to the other. 



Some of the ancients used the word in a more general sense, answer- 

 ing to change. Thus, according to them, creation, generation, corrup- 

 tion, increase, diminution, and change of place, are the six sorts of 

 motion. We have here no further to do with this than to remind our 

 readers, when they see local motion spoken of in old writings, that this 

 is the term by which simple change of place, to which the word 

 motion is now restricted, is distinguished from the other changes 

 which the same word then denoted. We still apply the word, as we do 

 terms of magnitude (see that word) to changes of the moral system, as 

 in speaking of the motions and emotions of the mind. 



If there be anything which would need neither definition nor 

 comment, it might be supposed to be simple motion, a thing never 

 absent from one moment of the waking perceptions, nor even of t ho 

 dream. Its existence was however denied, or is reported to have been 

 denied, by various of the Greek sophists, though it is highly probable 

 that some matter-of-fact historians have handed down as a deliberate 

 opinion what was merely meant for an ingenious attack on < 

 another established school. According to Sextus Empiricus (i. S 1 7), 

 Diodorus surnamed Cronus, a Carian, disproved the existen 

 motion as follows : If matter moves, it is either in the place in which 

 it is, or the place in which it is not ; but it cannot move in tin- 

 place in which it is, and certainly not in the place in which it is not : 

 consequently it cannot move at all. To which the first named author 

 replies, that by the same rule men never die, for if a man die, it must 

 cither be at a time when he is alive, or at a time when he is not alive. 

 A better answer would have been, that it is true of all material pheno- 

 mena that they happen either in the place in which the matter is, or 

 in that in which it is not, except only the change from that place in 

 which the matter is and will not be, to that in which it is not but will 

 be. The syllogism of Diodorus may be useful to remind u.s thnt 

 motion implies both spaces and times, since the sophism excludes the 

 latter from consideration. Zeno of Elca (not the Stoic) gave the 

 celebrated argument of Achilles and the Tortoise. [PROGRESSION.] 



If we conM<!< T ini'icly motion, without any reference to the matter 

 or the quantity of external force required to move it, we have, 

 as we conceive, a subject of pure mathematics before us, though this 

 has been contested. Newton however used considerations of motion 

 without hesitation in his fluxions ; and his successors have endeavoured 

 to avoid them by circumlocutions, which, however consonant they 



