1W 



BIRD'S-EYE VIKW. 



lilSCTIT-MANUFACTURE. 



at a peculiar subctatu if in, which may bo obtained in a 



purer form by repeatedly digesting the berries of the niUtletoe in 

 ether, and finally ex|lling the ether at a gentle hont. Yiscin i- n 

 white, tough, opaque, and very adhesive rosin, wlik-h <l"v in>t dry. 

 It U voluble in ether, eawntial oil*, and solution of jxitaah, but in- 

 soluble in alcohol and dilute acids. Nitric acid converts it into oxalic 

 acid and a solid fat Macaire-I'rinsep found it to consist of 



Carbon 7V6 



Ujrdrogtn 9-t 



OiTftn 15-2 



100-0 



The same cheuiist believes binllimo to be a mixture of viscin, 

 baasorin, and acetic avid, and that it does not exist in the plant* from 

 which it is procured, but is produced by fermentation. The viscosity 

 and toughness of viscin are so great, that when small birds alight upon 

 branches smeared with it, they cannot extricate themselves ; hence the 

 use of the impure substance by bird catchers. 



BIRD'S-EYE VIEW, a mode of perspective representation, which 

 may be divided into two kinds, proper and improper. The latter of 

 these, the one most generally employed, differs from ordinary perspective 

 delineation, in nothing else than in the horizon being taken much 

 higher than usual : the horizontal line, and of course the point of sight, 

 is either placed above the picture, or the level of the ground is sup- 

 posed to be considerably below the base of the picture. The objects 

 thus shown, whether buildings or landscape, or both combined, appear 

 as they would do if viewed from some lofty station, from the summit 

 of a building, from a terrace, tower, or any other eminence ; but still 

 the spectator is supposed to be looking in a straightforward direction, 

 and the plane of the picture to be perpendicular to the natural horizon. 

 Consequently, only distant objects can thus be shown, because, when 

 looking in that direction, a person cannot possibly see objects immedi- 

 ately beneath him. He can do that only by looking down upon them ; 

 but in a picture there can be but one Iiwtant of view, nor can the point 

 of sight be shifted at pleasure, by the eye being directed upwards or 

 downwards, so as to alter the field of vision, and take different objects 

 in succession. Whatever is shown in a picture must be supposed 

 capable of being embraced by the eye at once ; although in practice 

 some slight degree of licence in this respect is occasionally allowable. 



If it be desired to show the objects immediately below the spectator, 

 o as to give a distant view of the tops of buildings so situated, and of 

 ports that would otherwise be concealed from night, recourse must be 

 had to the first-mentioned mode, namely pruper bird't-ri/e perspective. 

 This is the reverse of that employed for ceiling-pieces, termed tli sotto 

 in in ; for as there objects are fore-shortened as seen from below, so in 

 the birdCt-cyc they are foreshortened, as if viewed from above. This 

 species of bints-eye might therefore with great propriety be distinguished 

 by the name of prone peripectire, or looking downwards ; and the ill 

 lotto in IK, by that of supine perspective, or looking upwards. In like 

 manner as in ceiling perspectives, the plane of the picture becomes 

 parallel to the natural horizon, instead of vertical, so does it in a proper 

 binl'f-'i/f view ; with this difference, that in the former case the eye is 

 beneath the picture and looking up to it ; in the latter over it, and 

 looking down upon it ; at least, if not exactly horizontal, the plane of 

 the picture must be more or less inclined, according as the eye is 

 supposed to look down more directly or obliquely ; because the plane 

 of projection or picture must be assumed as perpendicular to the central 

 ray from the eye. The relative position of objects to each other and 

 to the picture, and of the picture to the eye, are the same in this as in 

 ordinary perspective, the sole difference being that of the spectator's 

 own situation. This will be apparent if we look into a hollow cube, or 

 box, open on one side ; it matters not whether it be open on one of the 

 upright sides, or on the top. In either case the planes or sides perpen- 

 dicular to the open side, and the one parallel to, or facing it, will have 

 the same perspective appearance ; only in the one case the plane facing 

 the spectator will lie vertical, in the other horizontal. In a picture or 

 drawing this will depend entirely upon the artist whether he chooses 

 to represent the plane parallel to the picture as horizontal, that is the 

 ground or floor, and the other planes perpendicular to the ground ; or 

 that parallel plane and two of the adjoining planes upright, and the 

 other two horizontal. Again, were a hole bored through the ceiling of 

 a lofty room, a person looking down through it would have a perfect 

 or proper bird's-eye view, both of the apartment and its furniture. 

 Hence, it is obvious that in such representation the floor would answer 

 to what in the common mode of perspective would be the side or end 

 of the room facing the spectator; also that the vertical line." of tliu 

 side* of the room, of doors, windows, legs of chain, &c., would vanish 

 to some point in the line or plane passing through the eye, exactly as 

 the horizontal lines would do if they were seen according to the usual 

 position. For unless the lines, in this case intended to represent 

 upright ones, were made to vanish, those planes or walls woidd not lie 

 foreshortened ; and unless that were done they could not be viewe.l, 

 but the whole would be reduced to a mere plan of the room ; just as a 

 common upright view would be reduced to a section or geometrical 

 elevation, if the planes re|iresenting the other two walls with the ceiling 

 and floor were not shown perspectively or foreshortened. Yet, although 

 Mich perspective or bird's-eye view would be correct in itself, it would 

 acem too fanciful and unnatural, if not positively distort <1. l. 



the objects would be shown under such very different circumstances 

 from those according t whieh they are really seen; consequently, 

 such kind of views would bequite unpietoriol. nmf merely raatteriof curi- 

 osity. They might, indeed, occasionally be found useful as explanatory 

 diagrams, or drawings, whenever it should I.,- required to show the 

 effect of an interior, as beheld from a lofty upper Cillery, not viewed 

 in a croos or straightforward direction, but by looking down into the 

 lower area of the apartment. This prone pertpectin might also be 

 applied for the purpose of giving a map-like, yet graphic view of a 

 group of building* and their locality. A* a picture, however, such 

 view would be extravagant, although as a picture-map it won! 

 -in. thing to recommend it. Even the more usual kind ot l. : - 

 perspective, or view with a very elevated horizon, is by no mean* well 

 calculated for picturesque effect, since it brings those parte 

 edifice into view which are intended to be concealed, and otherwise 

 L i c:,t ly takes off from the architectural effect ; causing the building to 

 viewed to appear too much like a small model placed upon a table. 

 BIRDSMorTH. [Mon.mxo.J 



BIRTH. [I.SKANTK-IDE.] 



BISCUIT, in pottery, is a term used to denote porcelain as well an 

 the commoner kinds of earthenware at a certain stage of the manu- 

 facturing process. To render them fit for most purposes, it is neces- 

 sary tluit fictile wares should be covered with a vitreous glaze ; and 

 hence arises the necessity for subjecting them twice to the action of 

 heat in furnaces. The first baking is necessary in order to preserve 

 the shape and texture of the pieces ; seeing that they would otherwise 

 be altered in these respects through the absorption of the water from 

 the glaze, which must be used in a fluid form. Neither would it be 

 possible, for the same reason, to apply painting, or to transfer printed 

 patterns to their surfaces in the green state tlint is, previously to 

 firing. It is after this first baking, and previous to the :t\ 

 the glaze and of embellishments, that these wares receive the name <>f 

 biscuit, which is given from the resemblance which they bear in 

 colour and apparent texture to ship-bread. Strictly ni>cnking, tin- 

 name is a misnomer, seeing that these articles are not ' twice-baked ' 

 while in their biscuit state. The second firing is necessary in order to 

 vitrify the glaze, and to bring out the metallic colours which are used 

 for embellishing earthenwares. 



The heat of the first oven must be at letut equal to that cm, 

 for the vitrification of the glaze ; because, as soon as that degree of 

 heat to which earthenwares have been already subjected is (tossed, a 

 further degree of shrinking occurs, which would occasion the glaze to 

 crack and peel off an effect which will not be produced by a rep. 

 of the degree of heat that has been once applied. It is a prop 

 clay to contract when subjected to any degree of heat greater than it 

 has previously borne, but short of the point of fusion ; and it is another 

 property to continue at that same state of contraction at even 

 temperature which is not above the degree of heat to which it has 

 once been subjected, and by which its actual state of contraction 1. 

 been produced. 



Earthenware in the state 'of biscuit is permeable to water, which 

 however it imbibes without undergoing any alteration of texture. This 

 quality fits it for being used in the cooling of fluids, which effect is 

 produced through the rapid evaporation from the outer sin 



See further on this subject under POTTERY and Pom i i u\. 



Many beautiful statuettes have been produced in the Staffordshire 

 potteries during the last few years, from models by Bell ,ui.l 

 .sculptors, in materials more or less resembling biscuit-ware. 



BISCU1T-MANUFACTI UK. Biscuit (German, /,//.,.,-/, . Dutch, 

 Scheeptbefcliail ; Danish, Xl.-itt.-ti; //-<< Swedish ./,- French, 



Sucait; Italian, Kinmti-. Swinish, Ri:rn<-h<i. Hullrta ; Portu- 



guese, Jiigcwito ; RUSH, Hurt, fimrher ; Latin, Panit liifnrl 

 a kind of bread made usually in the form of flat cakes. This fortn is 

 given to biscuits to insure their being deprived of moisture in tin- 

 baking, which circumstance is necessary for preserving them I, 

 use during the continuance of long voyages. The use of this k - 

 bread on land is indeed pretty general as a matter of luxury : ' 

 sea, biscuits are an article of the first necessity, seeing that bn 

 the more ordinary form in which it is used on shore, would M 

 become mouldy and unfit for food. 



The name biscuit ('twice-baked') is evidently derived from the 

 nature of the processes to which this kind of bread was formerly sub- 

 jected. The two bakings then used arc no longer found necessary ; l.nt 

 the name, although thus rendered inappropriate, has Wii continued. 



We may confine our notice chiefly to that kind of biscuit which 

 forms a principal part of the food of seamen, ami which i- f. ir that 

 reason usually known as ship-bread or biscuit. When b 

 this use, biscuits are most commonly made of the meal of wheat in .m 

 which only the coarsest bran has been separated. It is hardly p. 



sound for any length of time. Tin- |>n jo.i.i'inn of sea-biscuit is carried 

 on as A substantive branch of l.uii.-s in .ilm<--t every port of ; 

 for vessels engaged in trading with ili.-lmit countries. 



The largest biscuit-manufactories are those maintained by g. 

 ineiit for supplying the navy. The scale upon which these are carried 

 on is such as to moke it of great importance to introduce into the process 



