356 FERGUSON'S LECTURES. 



A J\I for the beginnings of the signs 8 and n& Then, 

 setting one foot in the point D, and extending the other 

 to A, describe the curve A L for the beginnings of qr 

 and*^= ; and the signs will be finished. This done, lay 

 a ruler from the point A over tho sun's declination in 

 the arch R S T, (found by the following table) for every 

 fifth day of the year : and where the ruler cuts the line 

 FD G, make marks ; and place the days of the months 

 right against these marks, in the manner shewn by fig. 

 2. Lastly, draw the shadow line P Q parallel to the 

 occult line A B ; make the gnomon, and set the hours 

 to their respective lines, as in fig. 2. and the dial will be 

 finished. 



There are several kinds of dials, (fig. 4.) which are called 

 universal, because they serve for all latitudes. Of these, 

 the best one that I know, is Mr. Pardie's, which consists 

 of three principal parts; the first whereof is called the 

 Anuni- horizontal plane (A), because in the practice it must be 

 parallel to the horizon. In this plane is fixed an upright 

 pin, which enters into the edge of the second part B D, 

 called the meridional plane ; which is made of two pieces, 

 the lowest whereof (B) is called the quadrant, because 

 it contains a quarter of a circle, divided into 90 de- 

 grees ; and it is only into this part, near B, that the 

 pin enters. The other piece is a semicircle (D) adjusted 

 to the quadrant, and turning in it by a groove, for rais- 

 ing or depressing the diameter (E F) of the semicircle, 

 which diameter is called the axis of the instrument. The 

 third piece is a circle (G), divided on both sides into 24 

 equal parts, which are the hours. This circle is put 

 upon the meridional plane, so that the axis (E F) may 

 be perpendicular to the circle ; and the point C be the 

 common center of the circle, semicircle, and quadrant. 

 The straight edge of the semicircle is chamfered on 

 both sides to a sharp edge, which passes through the 

 center of the circle. On one side of the chamfered 

 part, the first six months of the year are laid down, ac- 



