STONE WORKING. 



STRAIGHT, STRAIGHT LINE, PLANE. 



812 



each cutter is that of a forcible blow ; the machine being intended to 

 operate upon the harder kinds of stone. Messrs. Hunter, of Manches- 

 ter, have devised a machine for cutting pavement-slabs. Twenty or 

 thirty cutters are fixed to the periphery of a revolving disc ten or 

 twelve feet in diameter. These machines are in use in Dean Forest ; 

 some of them will cut 250 square feet of pavement, 1J inches thick, in 

 ten hours. 



When marble or other stone has been cut into slabs, its further 

 working is effected by machines of various kinds. To reduce it to 

 narrow slips, it is exposed to the action of small circular cutters, 

 ranged parallel on one common axis ; the distances between the cutters 

 are made equal to the intended widths of the strips ; the marble is 

 slowly brought up to the revolving cutters by the action of pulleys and 

 weights. 



Circular pieces are cut from slabs by ingenious machines. Large 

 circles are cut by means of four cutters placed at the ends of the arms 

 of a horizontal cross ; the size of the cross determines the diameter of 

 the circle to be cut, and the curvature given to each cutter is made 

 correspondent thereto. When the frame or cross is made to rotate, 

 the four cutters follow one another in the same path, and speedily cut 

 out a circular piece. Smaller circles are cut by means of a hollow 

 cylindrical tool, something like a punch ; but it acts by continual rota- 

 tion, and not by blows. By a modification of this apparatus, round 

 pillars and hollow cylinders or tubes of stone may be cut. 



To produce mouldings, or similar symmetrical cuttings in stone, 

 various machines are employed. The turning-lathe is used for circular 

 objects. Iron cutters, with sand and water, are not used here ; but the 

 workman acts upon the stone with long, sharp-pointed instruments of 

 steel ; and when the shape has been thus roughly produced, it is finished 

 by gouges and other tools. Strips of stone or marble, such as those 

 used for chimney-pieces, have mouldings formed upon their surfaces 

 by different means. The cutters here are in fact grinding tools. They 

 consist of masses of iron, whose surfaces are circular, and have been 

 wrought into various forms, such as hollows, headings, ogees, &c. ; the 

 tool rotates rapidly in contact with the stone, which is brought up 

 close to it by a weight and pulley ; and thus a moulding is formed on 

 the surface of the strip of stone, a counterpart of that on the iron tool. 

 A workman applies sand and water to the iron tool. The apparatus is 

 shown in the annexed cut. 



Fig. 1. Marble Moulding Machine. 



Thu smoothing, grinding, and polishing of marble and stone are 

 effected by machines variously arranged. Largo slabs are ground by a 

 plate of cant-iron. The slab, placed horizontally, has a reciprocating 

 motion given to it ; the iron plate, resting upon it, has a kind of spiral 

 motion; and the two motions together enable the iron to act equally 

 on all parts of the stone. Sand and water are let down between the 

 two surfaces, through holes in the iron plate. Smaller surfaces of 

 tone or marble are ground by being held down by hand upon the sur- 

 face of a revolving iron table, kept moistened with sand and water. 

 The Karl of Caithness has recently devised a machine for dressing the 

 surface of Caithness rag slabs, a stone well fitted for street pavements. 

 About 30 iron bars are ranged parallel and vertical, each with jagged 

 teeth at the bottom ; a crank movement lifts them all to a certain 

 height, one after another, and lets them fall heavily ; the slab slowly 

 moves beneath them, so as to be subjected all over to an equal 

 amount of jagging or chipping. This produces a surface level but not 

 smooth. 



The |xilishing of marble requires tools different from those used in 

 grinding or smoothing. The tools are made of lead or some other 



heavy substance, and are faced with a peculiar kind of felt, which, 

 when wetted and rubbed to and fro by any convenient machinery 

 polishes the marble. For smoothing and polishing of carved marble, 

 or of small pieces shaped in any irregular way, small pieces of cast- 

 iron, gritstone, smooth stone, slate, &c., are used in various ways. 



STOP. [ORGAN.] 



STOPPAGE IN TRANSITU is the seizure by the seller of goods 

 sold on credit during the course of their passage (transitus) to the 

 buyer. This principle is said to have been established about 1690 in 

 the Court of Chancery (2 Vern., 203) ; and it has since been acknow- 

 ledged in the courts of common law. The transitus is defined to be 

 the passage of the goods to the place agreed upon by the buyer 

 and seller, or the place at which they are to come into the possession 

 of the buyer. This definition does not mean that the term tran- 

 situs implies continual motion : goods are in transitu while they 

 ;ire at rest, if they are still on the road to the place to which they 

 have been sent. This doctrine of stoppage in transitu entitles a seller, 

 who is empowered to step the goods before they come into the buyer's 

 possession. The right is not confined to cases of buying and selling. 

 A factor either at home or abroad, if he consigns goods to his principal 

 by the order of the principal and has got the goods in his own name 

 or on his own credit, has the same right of stoppage in transitu as if 

 he were the seller of the goods. Questions of stoppage in transitu 

 sometimes involve difficult points of law. The right of stoppage 

 implies that the goods are in the possession of the seller or factor when 

 he exercises this right. The exercise of the right is excluded in the 

 case of a bill of lading which has been endorsed over ; for here the 

 endorsement passes the property in the goods absolutely to the 

 endorsee. 



STOKAX. [STYKAX.] 



STORMS. [TORNADO; WHIRLWIND.] 



STOVE. [COOKING APPARATUS ; SMOKE, CONSUMPTION OF ; WARM- 

 ING AND VENTILATION.] 



STOVE-PLANTS. [HOTHOUSE.] 



STRABISMUS. [SQUINTING.] 



BTBAIOHT, STRAIGHT LINE, PLANE. There is no occasion 

 to define a straight line as matter of information ; so that we have 

 here only to consider the definitions which have been given and their 

 relative merits, taking them as attempts to produce a mathematical 

 description of straightness. 



There are three attempts at definition of a straight line ; by Plato 

 (or one of his immediate school), by Archimedes (as is said), and by 

 Euclid. The moderns have repeated these various forms, but have 

 not, to our knowledge, ever succeeded in producing a definition entirely 

 new which did not contain the defects of one or other of the three just 

 mentioned. 



The Platonic definition, according to Proclus, is as follows : " A 

 straight line is that of which the middle parts hide (^riirpoo-flti) the 

 extremities ; " a physical definition, owing its truth to the 'circumstance 

 of the rays of light proceeding in straight lines, and involving the 

 notion of straightness as a part of its own explanation. This defini- 

 tion has been little if at all used by geometrical writers. 



Archimedes defines a straight line as the shortest distance between 

 two points, or at least this definition is often attributed to him, but 

 not correctly. It is one of his postulates in the book on the Sphere 

 and Cylinder, that of all lines drawn between two points the least is 

 that which is straight : but he is too well judging a geometer to assign 

 such a property as a definition. The Arabs substituted the shortest- 

 distance description for the definition in Euclid, and accordingly our 

 earlier editions of Euclid do the same; nor was this flaw removed 

 until 1505, when Zainberti translated Euclid from the Greek. It has 

 often been supposed that this shortest-distance definition is good as a 

 definition, though not proper for a pupil in geometry, an opinion from 

 which we must dissent : for how is it known to those who are yet to 

 Icuni what a straight line is, whether there can be a shortest distance if 

 That is, how is it known- that there are not many distances between 

 two points, on different lines, which are severally shorter than any 

 other distance, and equal to one another ? The answer is, no doubt, 

 that the mind has a perfect conception of the impossibility of such a 

 thing ; and the rejoinder is yes, because the mind has a perfect con- 

 ception of a straight line : that is to say, the definition is only saved 

 from causing confusion by its own uselessness. Again, the supposition 

 that measurement of distances on all manner of curves is to be a pre- 

 liminary to one of the definitions of a science which treats no curve 

 but the circle, and does not succeed, by reason of certain limitations of 

 process, in measuring distance even on that one, is an incongruity. 



Euclid defines a straight line to be that which lies evenly (i( faov 

 Ktiriu) between its extreme pouits. The words Q taov have been trans- 

 lated ex tcyuo by Barocius, ex tequali by Zamberti, equally by Billingsley 

 (taking some of the oldest translations as specimens). The definition 

 wants precision, but the meaning is obvious. Two points being given, 

 the surrounding space may be viewed in all manner of relations to 

 those two points, as above or below, right or left, &c. The straight 

 line which joins the two points is that which is not more related to 

 one of these notions than to any other; and throughout its whole 

 length takes an even course, without a possibility of being claimed, so 

 to speak, by any one of the surrounding parts of apace rather than by 

 any other. 



