POHPHYRIC AC! P. 



PORTICO. 





seated by Sr of hydrogen gas, and a volume of oxygen ga, in equal 

 in vultiBM to Si- only. 



All roatrrul substances being subject to attractive forces. It has been 

 made quection whether the attractions which take place between the 

 molecule* of bodiei, and which aro Insensible at all appreciable 

 <tfaH"*-* from them, are the same aa that general attraction which 

 extends indefinitely through space ; modified, however, by the figure* 

 and mutual distances of the molecule*, by heat, electricity, .md i>crha|* 

 by powers which are at present unknown to us ; tmt, in order that this 

 hypothesis mar be admimble, the dimensions of the molecules of 

 bodies should be extremely Mnall compared with those of the gpace* 

 among them ; and the denaitiea of the molecules immenwly greater 

 than the densities of the bodies themselves. La Place estimates 

 ( SyiU-me du Monde,' ch. xviil 4th edit.) that a molecule of a spherical 

 form, whose diameter in one millionth part of a metre, ought to lu\. a 

 density more than six million time* as great as the mean density of 

 the earth in order that it might exercise an attraction equal to that of 

 terrestrial gravity ; and he observes, that the attractive forces exercised 

 by the molecules of bodies, which are probably only the excesses of 

 toe entire attractions of the molecules over the repulsive forces of the 

 caloric in the intervals, must bo vastly greater than that of gravity, 

 since the actions of the molecules of a body produce visible Inflexions 

 of tin- rays of light, which cannot be asserted concerning the attraction 

 of gravity. [ATTRACTION.] 



PORPHYBIC ACID. [KriASTiiic ACID.] 



PORPHYROXINE. [OPIUM, ALKALOIDS or.] 



rolUtlOO, Hint/mm*, is a pustular and contagious disease of the 

 scalp, or, hi some rare cases, of other parts where there is much hair. 

 M. Biett describes two varieties of it under the names of /'. farota and 

 /'. *futttlala. Dr. Willan described many more varieties, but he 

 included in this name other widely different diseases, 



Porri'jo farnm consists of an eruption of small flat yellow pustules, 

 with depressions at their centres, distinct or clustered, and which 

 soon concrete into bright yellow honey-coloured scabs, on the surface 

 uf which the depressions of the centres of each pustule are usually .-till 

 visible. After some time the scabs become thick and white ; and 

 drying, split and break off. Sometimes, however, they remain long 

 adherent, the skin beneath them ulcerating, and the discharge oozing 

 through them. The hair of the parts affected is .always much 

 loosened, and often falls off spontaneously ; and, when it grows again, 

 is weaker and lighter in colour than before. 



Porrigo favosa appears rarely in any part except the scalp. It 

 affects persons of all ages; but especially children from six to ten 



fears old, and those who are naturally unhealthy, or ill-fed and dirty. 

 t is distinctly communicable by contagion, and by this means may 

 affect alike the weak and the robust. 



It ia one of the most obstinate diseases of the skin, and often lasts 

 for months or years. The first measure for its cure is to cleanse the 

 hf.nl completely with poultices or soap and water, and to have the 

 hair cut very close. The dead hair and scabs must than be cleaned 

 off as fast as they form. The medicines that promise the speediest 

 success are lotions with sulphuret of potash or slightly acidulated, or 

 with alkalies or their carbonates, such as in the following forms : ten 

 grains of potassa fusa in an ounce of water, to be applied occasionally ; 

 one or two drachms of subcarbonato of potash in a pint of water, to 

 be constantly applied on linen ; or from one to three drachms of sul- 

 phuret of potash to a pint of water ; or from ten to twenty drops of 

 any of the mineral acids to a pint of water, also to be constantly 

 applied. Lotions also of sulphate of copper, nitrate of silver, and of 

 nearly all the stimulant and astringent nalts, have been employed, and 

 sometimes with success ; and in most cases of the disease, all these 

 will have to be tried in turn, till one, being found beneficial, is con- 

 tinued till the cure is completed, or till it has ceased to do good, when 

 it must be changed for another. Internal medicines must be employed 

 if there be any symptoms Indicating their necessity ; but generally they 

 



Porrigo Kuluiata, which is more commonly termed ringicorm than 

 the preceding, appears in the form of circular red patches, with 

 numerous minute yellow pustules with depressed centres, out of which 

 a hair usually projects, and which are attended by great itching. The 

 fluid contained in the pustules dries up soon after they are formed, 

 and, by coalescing, they produce a scab over the whole diseased surface. 

 Subsequently successive cro| of new pustules form around the 

 margin of the cab, which is increased by their drying, and tlpi- the. 

 diwase may spread over the greater part of the scalp l.y the meeting 

 and coalescing of the patehcn, which were at first i !.''.!. TL. hair 

 usually falls off from the part affected, or is lal it may hi- 



pulled out without p.iin. 



Thin form of porrigo sometimes appears spontaneously in poor and 

 dirty children, but it is usually produced by contagion. The suggestions 

 for tU treatment must be the same as fur Porrigo favosa. 



I'-iKTiWi,,-.. [WiXfcJ 



MS, m fortification, is a barrier formed of several large 

 pieces of wood, joined across one another like a harrow, and each 

 j. ;ntI with iron at the bottom. A portcullis was generally hung 

 over the gateways of old fortified towns, ready to let down in case 

 of a surprise, when the gates could not be shut. (James's ' Military 

 Dictionary. 1 ) The French, at a very early period, called it " porte- 



, n] 



tnt," that in, sliding gate, which is the true f the 



.ise" U likewise used by r the 



Iirtcullis, whence our term is immediately derived. 



PORTER. [BIIMVIM;.] 



PnllTFIKE is a composition consisting of ,!phnr, and 



mealed gunpowder, mixed together by living nibbed betw, 

 hands, and, after being passed through hair-sieve*, iimi.-t ..-.! with 

 spirits of wine: the mixture is then rammed or driven into :. 

 co*u of a cylindrical or conical form, and less than an inch in din- 

 A piece of portfire sixteen inches long will I'urn fioin t 

 fifteen minutes. 



It is generally used as a match for firing artillery, in which case 

 the saltpetre, sulphur, and powder are In Up proportion of >:. 

 1, respectively; but it is frequently employed in tiring min. 

 blasting rocks, when the proportions of the like ingredients - 

 7, 2, and !v y. For these lost purposes the i>rtfirc is 



attached at the extremity of the train, or is inserted in tin 

 bored in the rock or object to be blasted ; and the fire is applied to it 

 by a in 



POKTK'O. Originally applied without distinction t- 



mihulatimrx, the : i,:nif) a -li 



space enclosed by columns at the entrance to a building : 

 otherwise expressed, roofed with a pediment, lil. >r front of a 



Grecian temple. The term therefore, as now generally rent: 

 answers to the Pronaot of such a temple. 



According to the number of columns in front, porticos are said to be 

 telraftijle, that is, with four columns; heJOttyle, ssith ci\ 

 with eight; dtcattyle, with ten; and < with tssel 



greatest number that can very well be brought beneath a pediment; 

 and even of these two last the examples are exceedingly rare. If 

 instead of columns at the angles there are antic [AqrXJj then the 

 number of columns alone aro reckoned as before, and 

 what is equivalent to a portico containing two more : thus a <iiV 

 aulli, that U, two columns between two ant.i-, is njual to a teti. 

 as in l.oth there arc three intercolumns ; a tctnulyle in 

 to a hexastyle, and so on. By means of this simple modo of numerical 

 notation, a couple of words suffice to explain in the concisest manner 

 what even a long description may leave doubtful : for instance, when 

 wo say that a portico is hexastyle Ionic, we clearly sp< vify the 

 and the number of columns in front ; and it is upon i 

 Stance that so much of particular character du|>ondN. l>y way f 

 example, we instance the following structures : distyle in antis, the 

 church in North Audley Street ; the entrance to the North -Western 

 Railway Terminus, Euston Square, is a magnificent example of a 

 distyle in antis, though not being an entrance attached to a building, 

 it is rather apropyhcum than a portico. Tetrastylo, portico of 1! 

 Chapel, Regent Street ; tetrastylo in antis, Law Institution. Hex 

 itieos of St. Martin's; St. George's, Hanover Squai. 

 Pancras; Post Office; Italian Opera House, ('..sent Harden. Octa- 

 utyle, portico of Royal Exchange; British Museum; the National 

 Gallery ; and decastyle, that of London University C. ' 



Pni-tli'iin arc called //) '.<(y/r when, as generally happens, they p 

 front the main building. Such as are I'M antit, and recessed within the 

 front of the building, are technically called l<*jylai ; the latter term 

 indeed is not always employed in this particular sense, Imt it would be. 

 convenient it it were, a* much ambiguity would thcrel.y IK; prevented. 

 The New Town Hall, Leeds, haa a decastyle loggia. Altli\ui 

 a loggia so far resembles any other colonnade, it differs from it 

 in being situated, like a portico, at the entrance and in the 

 facade, whereas colonnades arc usually lengthened ranges of column- in 

 other situations; thus we speak of the "colonnades " of tin- Louvre, of 

 Greenwich Hospital, and of the pia//a of St. IVtcr's at Rome. 



Pteudu-prostyle is a useful term suggested by Mr. Husking for such 

 an arrangement of columns beneath a pediment as resembles a prostyle 

 iu elevation, but which, instead of advancing forssanls forms merely a 

 slightly projecting break, the portico itself being within the building, 

 and nosvise differing from a recessed loggia, except that it is not in 

 unlit, and is crowned by a pediment. Of this kind is the Ionic portico 

 of the East India House, which, instead of U-ing a tetrastyle in antit, 

 is converted into a hexastyle by placing six columns in such manner 

 that the end ones come immediately before the antae or pilasters. The 

 front of the Law Institution, Chancery Lane, may also be called 

 pseudo-prostyle, because, although a loggia in atitie, it is surui. 

 l>y a pcdim> 



Even in prostyle porticos there is great difference of character m 

 as regards the degree of projection given to them, independently of 

 th. i ein Min.-tan. - ; I m .ire made to advance a single intcrcohmm, 

 and ..' ' il.ly more. At the risk then i 



appearing to innovate upon the terminology of architecture, ssc would 

 propose the following terms : mon(y>rottyle, wl i ojects 



only one intercolumn, as the lonio hexastyle of St. Pancras church, 

 I. ..iid. .11 ; ili^ri-tti/l' , where the projection is two intercolumns, a in 

 the porticos of St. Martin's, Charing Cross, and St. George's, I'.i 

 bury, and HO on; by which method the portico of the i'anth. 

 Rome might be briefly yet distinctly described as a Corinthian octa- 

 style tripru f i;il(, that is, a prostyle with eight columns or fceven 

 intercolumns in front, and three open intercolumns at its ends. 

 Another circumstance, which it is highly important to note, is whether 



