OF DIALING. 377 



given ; and thence the angle D Wd is found, and so is LECT 

 the hypothen use Wd. Again, the difference, or the ^ : x 

 sum, of D Wd and D W R, the elevation of the equi- 

 noctial above the horizon of D, gives the angle d W R, 

 and the hypothenuse of the triangle W R d was just now 

 found; whence the sides Rd and WR are found, the 

 former being the latitude of the place d, and the latter 

 Ihe complement of R Q, the difference of longitude 

 sought. 



Thus, if the latitude of the place Z be 52* 10' north ; 

 the declination S D of the plane Z h (which would be 

 horizontal at d) be 36, and the reclination be 15, or 

 equal to the arc D d ; the south latitude of the plane d, 

 that is, the arc R d, will be 15 9' ; and R Q, the differ- 

 ence of the longitude, 36 '. From these data, there- 

 fore, let the dial (fig. 4.) be described as in the former 

 example. 



8. Only it is to be observed, that in the reclining or 

 inclining dials, the horizontal line will not stand at 

 right angles to the hour-line of XII, as in erect dials ; 

 but its position may be found as follows. 



To the common substilar line C K L, on which the 

 dial for the place d (in the preceding engraving, page 

 376) was described, draw the dial Crpm 12 for the 

 place D, whose declination is the same as that of d (viz. 

 the arc 5 D :) and H O, perpendicular to C m, the hour- 

 line of XII on this dial, will be a horizontal line on the 

 dial CPRM XII. For the declination of both dials 

 being the same, the horizontal line remains parallel to 

 itself, while the erect position of one dial is reclined or 

 inclined with respect to the position of .the other. 



Or, the position of the dial may be found by applying 

 it to its plane, so as to mark the true hour of the day 

 by the sun, as shewn by another dial ; or by a clock, 

 regulated by a true meridian line and equation table. 



9. There are several other things requisite in the 

 practice of dialing; the chief of which I shall give in 



