378 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[November, 



with regard to its flat foot or base, B C, that it keeps the point A 

 always perpendicular to the plane D E of the drawing-board at the 

 point B ; thus the line A B, in every position whatever of the sliding 



Fig. 1. 



drawer, ABC, keeps always parallel to itself; and, therefore, if a 

 pencil is placed at B, whatever A traces at one end is drawn exactly 

 at the other by that pencil. If A traces the contour A F, B draws the 

 contour at B L. When it is requisite to draw another contour the 

 drawing-board is screwed back the distance required by the adjusting 

 screws II H, then the point A will trace another contour, A F, which 

 of course is drawn at B L as before. In this way the whole solid, G, 

 may be traced over. It is hardly necessary to notice that if a metal 

 plate be substituted for the drawing paper, and a grater for the pen- 

 cil, we may secure an engraving plate, whence copies may be taken. 



By this apparatus profiles of the countenance, of architectural 

 mouldings, and models of maps, may be taken without the use of the 

 screw; and if constructed on a large scale, the lines of a boat, &c, 

 may be taken with ease and expedition. 



If it be desirable to make a drawing having the effect of a picture, 

 the contours should be drawn close and blunt; but if a measurement 

 drawing, they must be wider apart and sharp, so as to produce no 

 confusion when the back parts are traced over. 



Fig. 2 represents a plan of a piece of land with three hills laid 

 down in contours from a model ; each contour is a representation of 

 the surface at certain given perpendicular distances, say one inch of 

 the model ; then, by taking the outer contour as the base or datum, 

 each contour within will represent so many inches perpendicular 

 above the base ; it will thus be seen that the height of the three hills 

 in the model by the annexed plan are respectively 6, 7, and 8 inches 

 above the base. 



If it is requisite to rind the distance on the surface between A and B, 

 I. e. how far they are apart in the original model. From B or A, as is 

 most convenient, draw a perpendicular BC equal in height to all the 

 sections between A and B, then will the line AC be the distance on 

 the surface between A B. 



Suppose it be required to make a section of a cast from P to Q, of 



which rig. 2 is a drawing, it will be first necessary to draw perpen- 

 diculars from the several intersections of PQ with the contours by 

 means of parallel rulers, and then taking P' Q' for P(j at a distance 



Fig. 2. 



from the drawing, to avoid confusion, draw parallel lines to it distant 

 from each other the height of each section. Where the former inter- 

 sect the latter, draw the outline PTRS (i, which will give the sec- 

 tion required. In the same manner a measure may be taken from the 

 back to the front also, because the machine can draw, if necessary, the 

 contours at the back within the same space as those of the front, and 

 thus a solid object is drawn back and front from one point of view, 

 and measured in every possible direction. 



I have the honour to be, Sir, 



Your most obedient servant, 



Salter Livksat, M.D., R.N. 



GTPSOGRAPHtC SKETCHES' PROSJ TUB PRIORI CHURCH OF 

 ST. BARTHOLOMEW, SMITIIFIEED. 



With ii Gypsoffrnphic Drawing, Plate XiV. 



Among the great facilities which the metropolis affords for a school of 

 architecture, must not he omitted the many monuments of different styles 

 which it possesses. With regard to the early periods of English architecture, 

 many admirable specimens exist, which, although abounding in points of 

 interest, are not adequately studied— in some cases, indeed, are not adequately 

 known. Many of these, from their recent restoration, have, it is true, at- 

 tracted public notice, but many others, of no less merit, remain in compara- 

 tive obscurity or neglect. To enumerate all the metropolitan works of the 

 middle ages would he impossible, but to remind the student that they are 

 not contemptible, we may call to his notice Westminster Abbey and the 

 Chapter House, Westminster Hall and St. Stephen's Chapel, St. Mary Overy's, 



1 This method of Engraving (of which our present Journal contains several 

 specimens, particularly those in this article of the Priory Church of St. Bar- 

 tholomew the Great,) is a recent invention which bids fair, if it continues to 

 progress with as rapid strides as it recently has done, to effect a very con- 

 siderable revolution in the art of engraving, more especially in that depart- 

 ment of the art termed wood engraving, or engravings printed from the sur- 

 face at the type press. Our readers are doubtless aware that in the latter 

 process a drawing is made by the artist upon a piece of box wood in pencil, 

 I and that those portions of the wood or block uncovered by the drawing are 



