SEWING MACHINES 761 



it being extracted, the juice is to be dried as quickly as possible, because it runs 

 rapidly into putrefaction. Though insoluble in water, it is extremely diffusible 

 through it, and is very slowly deposited. Caustic alkalis dissolve the sepia, and turn 

 it brown ; but in proportion as the alkali becomes carbonated by exposure to air, the 

 sepia falls to the bottom of the vessel. Chlorine blanches it slowly. It consists of 

 carbon in an extremely-divided state, along with albumin, gelatine, and phosphate 

 of lime. 



The dried native sepia is prepared for the painter by first triturating it with a little 

 caustic lye, then adding more lye, boiling the liquid for half an hour, filtering, next 

 saturating the alkali with an acid, separating the precipitate, washing it with water, 

 and finally drying it with a gentle heat. The pigment is of a brown colour, and a 

 fine grain. 



SEPTARXA (from septum, ' a division '), called anciently Indus Heltnoiitii (the quoits 

 of Van Helmont, from their form), are argillo- calcareous concretions intersected by 

 veins of calc-spar, which, when calcined and ground to powder, form an excellent 

 hydraulic cement. 



From the regular arrangement of cracks in septaria which generally assume pen- 

 tagonal forms resembling in appearance the divisions in the shell of a tortoise, they 

 have received the common name of ' turtle-stones ' or ' fossil tortoises.' The turtle- 

 stones found in the Oxford clay at Weymouth, when cut into slabs and polished, form 

 very handsome tables. The number of veins of calc-spar, upon which their beauty 

 depends, renders these turtle-stones unfit for forming an hydraulic cement, in conse- 

 quence of their furnishing too great a quantity of lime when calcined. Septaria fit 

 for furnishing cement are dredged in large quantities in Chichester harbour, and off" 

 the coast of Hampshire, and are also procured from Harwich, Sheppy, and several 

 other places. A stratum of septarian stone, forming the Broad Bench on the coast 

 of Dorsetshire, affords an excellent cement, and is largely quarried. H. W. B. 



SERPENTINE is a mineral of the magnesian family, being a hydrated silicate of 

 magnesia, composed of silica 43'64, magnesia 43'35, water 13-01 = 100. Its colour 

 is either green or a mixture of red and green, seldom of a uniform tint, but generally 

 of several shades, arranged in dotted, striped, and clouded forms. For this reason it has 

 received the name of serpentine (or ophiolite, from Gr. 8<(>is, ophis, 'a serpent,' and \iOos, 

 lithos, ' stone '), from the fancied resemblance which it bears to the skin of a serpent, 

 both in colour and in its spotted or mottled arrangement. Specific gravity, 2'5 to 2-6. 

 It is slightly unctuous to the touch, sectile, and tough, and therefore easily cut into 

 ornamental forms. It has been divided into precious or noble serpentine, comprising 

 the purer translucent and massive varieties, with a rich olive-green coloiir ; and common 

 serpentine, or the opaque varieties, forming extensive rock masses, like those of the 

 Lizard in Cornwall, of Anglesea, Portsoy in Banffshire, Unst and Fetlar in Shetland, 

 and Zoblitz in Saxony. 



Serpentine, though so soft as to be scratched by calcareous spar, and to be turned 

 in the lathe, takes a good polish, and forms a very beautiful ornamental stone. At 

 Zoblitz it has long been manufactured into a variety of articles, which find their way 

 all over Germany ; and works have been established in Cornwall, where, by means of 

 powerful machinery, it is made into columns, vases, chimney-pieces, and other orna- 

 mental articles which have been rather extensively used. The serpentine of Portsoy 

 is also a very beautiful stone, and was formerly exported for manufacturing into 

 similar objects. The Cornish serpentine and steatite were at one time sent to Bristol 

 in considerable quantities, where they were used in the manufacture of carbonate of 

 magnesia. H. W. B. 



SESAIVZU1VX OIXi, or Teel Oil. An oil produced from the Sesamum orientate, 

 which yields the seeds known as teel seeds. It is of a peculiarly bland nature. 



SEWING MACHINES. The history of these ingenions inventions has been so 

 well told by Professor Willis, in his Eeport on the machinery for woven fabrics of the 

 Paris Exhibition, that we do not hesitate to borrow from it. 



At the Paris Exhibition in 1854, fourteen exhibitors came provided with sewing 

 machines. They were of different characters, and have been divided by Mr. Willis 

 into four classes. 



Under the first class came the machines in which the needle is passed completely 

 through the stuff, as in hand-working : ' It is so natural, in the first attempts to make 

 an automatic imitation of handiwork, that the imitation shall be a slavish one, that we 

 need not be surprised to find the earlier machines contrived to grasp a common 

 needle, push it through the stuff, and pull it out on the other side.' 



Thomas Stone and James Henderson, and some others, patented machines of this 

 kind, which proved abortive. M. Heilmann exhibited an embroidering machine in 

 1834, in which ' 150, more or less, of needles are made to work simultaneously, and 

 embroider each the same flower or device upon a piece of stuff or silk stretched in a 



