PHANTASMAGORIA 551 



depend on increased economies in fuel, mining, and labour. On the other hand, the 

 abundance of petroleum in America, and the ease with which it is obtained, will, 

 unless new uses for the material are discovered, keep the trade only barely lucrative. 

 PE-TITN-TSE is the Chinese name for what is thought by geologists to be a 

 partially-decomposed granite, used by them in the manufacture of their porcelain. 

 It is analogous to our Cornish china-stone. See CHINA STONE ; CIAY. 



PETWORTH IVXARBIiE. A shelly limestone, occurring in the "VVealden strata, 

 in the neighbourhood of Petworth, in Sussex. See SUSSEX MARBLE. H. W. B. 



PEWTER. (Potier detain, Fr.) Pewter is, generally speaking, an alloy of tin 

 and lead, with a little antimony or copper, combined in several different pro- 

 portions, according to the purposes which the alloy is to serve. The English 

 pewterers distinguish three sorts, which they call plate, trifle, and ley pewter : the 

 first and hardest being used for plates and dishes ; the second for beer-pots ; and the 

 third for larger wine measures. The plate pewter has a bright silvery lustre when 

 polished; the best is composed of 100 parts of tin, 8 parts of .antimony, 2 parts of 

 bismuth, and 2 of copper. The trifle is said by some to consist of 83 parts of tin, and 

 17 of antimony; but it generally contains a good deal of lead. The ley pewter is 

 composed of 4 parts of tin and 1 of lead. The English ley pewter contains often much 

 more than 20 per cent, of lead. As the tendency of the manufacturer is to put in as 

 much of the cheap metal as is compatible with the appearance of his alloy in the 

 market, and .is an excess of lead may caxise it to act poisonously upon all vinegars 

 aud many wines, the French Government appointed Fourcroy, Vauquelin, and other 

 chemists, to ascertain by experiment the proper proportions of a safe pewter alloy. 

 These commissioners found that 18 parts of lead might, without danger of affecting 

 wines, &c., be alloyed with 82 parts of tin ; and the French Government in con- 

 sequence passed a law, requiring pewterers to use 83-J of tin in 100 parts, with a 

 tolerance of error amounting to l-J- per cent. This ordonnanco, allowing not more 

 than 18 per cent, of lead at a maximum, has been extended to all vessels destined to 

 contain alimentary substances. A table of specific gravities was also published, on 

 purpose to test the quality of the alloy; the density of which, at the legal standard, 

 is 7'764. Any excess of lead is immediately indicated by an increase in the specific 

 gravity above that number. 



Britannia inetal, the kind of pewter of which English teapots are made, is an alloy 

 of equal parts of brass, tin, antimony, and bismuth ; but the proportions differ in 

 different workshops, and in many much more tin is introduced. Queen's metal is 

 said to consist of 9 parts of tin, 1 of antimony, 1 of bismuth, and 1 of lead; it serves 

 also for teapots and other domestic utensils. 



A much safer and better alloy for these purposes may be compounded by adding 

 to 100 parts of the French pewter, 5 parts of antimonj', and 5 of brass to harden it. 

 Under TIN, will be found the description of an easy method of analysing its lead alloys. 

 The pewterer fashions most of his articles by casting them in brass moulds, which 

 are made both inside and outside in various pieces, nicely fitted together, and locked 

 in their position by ears and catches or pins of various kinds. The moulds must be 

 moderately heated before the pewter is poured into them, and their surfaces should 

 be brushed evenly over with pounce-powder (sandarach) beaten up with white-of-egg. 

 Sometimes a film of oil is preferred. The pieces, after being cast, are turned and 

 polished ; and if any part needs soldering, it must be done with a fusible alloy of tin, 

 bismuth, and lead. 



It is the practice, however, in the metal works of Birmingham, to raise various 

 articles, as tea-pots, milk-jugs, and the like, from the flat into their proper forms, by 

 a process culled SPINNING : this consists in bringing the sheet of pewter against a 

 rapidly-revolving tool, by which, with a little dexterity on the part of the workman, 

 it is gradually fashioned. 



PHANTASMAGORIA. The phantasmagoria lanterns are a scientific form of 

 magic lantern, differing from it in no essential principle. The images they produce 

 are variously exhibited, either on opaque or transparent screens. The light may bo 

 a kind of solar lamp, but in most cases the oxyhydrogon or lime light is now em- 

 ployed. The manner in which the beautiful melting pictures called dissolving views 

 are produced, as respects the mechanism employed,, deserves to be explained. The 

 arrangement adopted in the instrument is the following : Two lanterns of the same 

 size and power, and in all respects exactly agreeing, are arranged together upon a 

 little tray or platform. They are held fast to this stand by screws, which admit of a 

 certain degree of half-revolving motion from side to side, in order to adjust the foci. 

 This being done in such a manner that the circle of light of ench lantern falls precisely 

 tipon the. same spot upon the screen, the screws are tightened to the utmost exteut so 

 as to remove all possibility of further movement. The dissolving apparatus consists 

 of a circular tin plate japanned in black, along three parts of the circumference of 



