POTTING 



day arc generally emptied the next, 

 the duration of fire only being 

 about eight or nine hours. Some 

 highly decorated pieces require re- 

 peated fires in both oven and kiln, 

 going again and again with addi- 

 tional artistic burdens upon them 

 until completed to the satisfaction 

 of the designer. 



Salt glazed ware or stoneware is 

 familiar to most on such common 

 articles as drain-pipes or ginger- 

 beer bottles. The invention dates 

 from about the 12th century, and 

 consists in exposing the clay article 

 to the intense heat of an open oven 

 or kiln, no protection being placed 

 between the fire and the clay ; 

 then when the ware is almost at 

 white heat, a quantity of common 

 salt is thrown upon the fires and 

 dropped through holes in the dome 

 of the oven. Volatilisation takes 

 place, and the salt vapour clings 

 around the ware ; the silica in the 

 clay combines with the sodium from 

 the salt, forming a thin glass glaze 

 on the surface of the piece, while 

 the chlorine, being set free, escapes. 

 H. Barnard 



Bibliography. History of Pottery 

 and Porcelain, J. Marryat, 3rd ed. 

 1868 ; History of Ancient Pottery, S. 

 Birch, 1873 ; History of Ceramic Art, 

 A. Jacquemart, Eng. trans. Mrs. B. 

 Palliser, 1873; Bow, Chelsea, and 

 Derby Porcelain, W. Bemrose, 1898; 

 Pottery and Porcelain, F. Litchfield, 

 new ed. 1900 ; Old English Porce- 

 lain and its Manufacture, 1903 ; 

 French Faience, M. L. Solon, 1903 ; 

 English Earthenware and Stone- 

 ware, W. Burton, 1904 ; Porcelain, 

 E. Dillon, 1904 ; The First Century 

 of English Porcelain, W. M. Binns, 

 1906 ; Chats on Old China, A. Hay- 

 den, 2nd ed. 1906 ; Lustre Pottery, 

 Lady Evans, 1920; A General His- 

 tory of Porcelain, W. Burton, 1921. 



Potting. Placing plants either 

 from the open ground or seed boxes 

 in pots, usually for the purpose of 

 cultivation under glass. Both pots 

 and saucers, before using, should 

 be scrubbed inside and out, to en- 

 sure cleanliness and proper porosity 

 of the pots. To secure the neces- 

 sary drainage, the pot should be 

 filled to about one-third of its 

 depth with pieces of broken pots, 

 chips of brick, oyster-shell, broken 

 charcoal, etc. The usual potting 

 mixture is loam and leaf mould, 

 with a liberal mixture of sand, the 

 latter inducing the plant to throw 

 out fresh roots. See Gardening. 



Potton. Market town of Bed- 

 fordshire, England. It is 11 m. 

 from Bedford, with a station on the 

 L. & N.W. Ely. The old church 

 of S. Mary has a Norman font. 

 The industries include engineering 

 works and the making of leather, 

 parchment, and beer. Potton was 

 formerly a centre for straw-plait- 

 ing and lace-making. Pop. 2,2 f J. 



6301 



Pott's Fracture. Fracture of 

 the lower end of the fibula. It is 

 associated with injury of the lower 

 articulation between the tibia and 

 fibula, the two long bones between 

 the knee and the ankle. 



Potts town. Bor. of Pennsyl- 

 vania, U.S.A., in Montgomery co. 

 It stands on the Schuylkill river, 

 39 m. by rly. N.W. of Philadelphia, 

 and is served by the Philadelphia 

 and Reading and Pennsylvania 

 rlys. It has important iron and 

 steel industries, also engineering 

 works, rolling mills, foundries, and 

 machine shops, and manufactories 

 of silk, hosiery, bricks, and agricul- 

 tural implements. Originally called 

 Pottsgrove, Pottstown was founded 

 in 1752, and incorporated in 1815. 

 Pop. 17,400. 



Pottsville. City of Pennsyl- 

 vania. U.S.A., the co. seat of 

 Schuylkill co. It stands on the 

 Schuylkill river, 35 m. N.N.W. of 

 Reading, and is served by the 

 Philadelphia and Reading and other 

 rlys. Picturesquely situated on the 

 declivity of steep hills, it is much 

 visited by tourists and is the centre 

 of an anthracite region. Among in- 

 dustrial plants are rly. workshops, 

 boot and shoe and shirt factories, 

 and textile and silk mills. Its build- 

 ings include the co. courthouse 

 and a public library. Pottsville 

 was settled about 1800, and was 

 made a corporate town in 1828. 

 Pop. 21,900. 



Potwalloper. Name formerly 

 given in certain English boroughs 

 to the man entitled to vote at par- 



Potting. Sectional views showing, 



left, correct method of placing 



broken pots ; right, position of 



plant when potting 



liamentary elections. The origin of 

 the word is doubtful, but it has 

 some connexion with the right of 

 boiling a pot, i.e. the right to a fire 

 and hearth, this giving the right to 

 the franchise. There were potwal- 

 lopers in Taunton until their rights 

 were extinguished by the Reform 

 Act of 1832. 



Pouched Rat (Geomys). Genus 

 of about eight species of burrowing 

 rodents of the family Geomyidae. 

 They are natives of North and Cen- 

 tral America. They have small eyes 

 and ears, and fur-lined cheek 

 pouches opening to the exterior. 

 The fore-feet have strongly deve- 

 loped claws fitting them for dig- 

 ging. The best known species is the 

 pocket gopher (q.v.). 



POUDRE B 



Poudre B. Propellant used in 

 the French service. It was invented 

 by P. M. E. Vieille, and the French 

 government adopted it in 1884 for 

 the Lebel rifle, this being the first 

 successful use of smokeless powder 

 in rifled firearms. The designation 

 Poudre B is derived from the 

 initial of the name of General 

 Boulanger, who was minister of 

 war when the powder was intro- 

 duced. It has always consisted of a 

 mixture of nitrocelluloses, of which 

 some are soluble and the remainder 

 insoluble in a mixture of ether and 

 alcohol, but the composition has 

 varied from time to time, the 

 Poudres BN (N standing for 

 nouveau) containing barium and 

 potassium nitrates, but at the 

 present time the propellant con- 

 tains no ingredients other than 

 nitro-cellulose and a stabiliser. 



For the manufacture of Poudre 

 B, two varieties of nitrocellulose 

 (g.v.) are prepared, the Abel, 

 Thompson, displacement and cen- 

 trifugal processes all being em- 

 ployed in one or other of the 

 factories. The products are known 

 as CP, and CP, (CP meaning 

 colon powrfre=nitrocotton), the re- 

 spective nitrogen contents being 

 13 p.c. and 12 p.c., the former 

 being only slightly soluble (about 

 8 p.c.) in ether alcohol mixture, 

 while the latter is almost com- 

 pletely soluble. The proportions of 

 the two nitrocelluloses vary, the 

 quantity of CP 3 being 20 p.c. to 

 55 p.c. of the mixture. 



The stabilisation of this pro- 

 pellant was a source of trouble at 

 one time, the internal explosions 

 which sank the lena in 1907 and 

 Libert e in 1911 being attributed to 

 this cause. At that time amyl 

 alcohol was employed to stabilise 

 the powder, but it is not very 

 effective for this purpose, as it does 

 not readily absorb the acids 

 released by the slow decompo- 

 sition of nitrocellulose, and it has 

 a tendency to form acid products. 

 In consequence the use of amyl 

 alcohol has been replaced by 

 diphenylamine, about 2 p.c. of this 

 compound being dissolved in the 

 solvent before the nitrocellulose is 

 incorporated. This appears to have 

 overcome all defects. See Ammu- 

 nition; Cartridge; Collodion Cot- 

 ton ; Explosives ; Nitrocellulose. 



Pouched Bat. The American rodent 

 with large cheek pouches 



