354 FERGUSON'S LECTURES. 



LF.CT. To rectify this dial, set the thread in the slit right 



-rf'-v-x-' a g ams t the day of the month, and stretch the thread 



from the day of the month over the angular point where 



the curve lines meet at XII ; then shift the bead to that 



point on the thread, and the dial will be rectified. 



To find the hour of the day, raise the gnomon (no 

 matter how much or how little) and hold the edge of the 

 dial next the gnomon towards the sun, so that the upper- 

 most edge of the shadow of the gnomcn may just cover 

 the shadoiu-line ; and the bead then playing freely on 

 the face of the dial, by the weight of the plummet, will 

 shew the time of the day among the hour-lines, as it is 

 forenoon or afternoon. 



To find the time of sun-rising and setting, move the 

 thread among the hour-lines, until it either covers some 

 one of | them, or lies parallel betwixt any two ; and then 

 it will cut the time of sun-rising among the forenoon 

 hours, and of sun-setting among the afternoon hours, on 

 that day of the year for which the thread is set in the 

 scale of months. 



To find the sun's declination, stretch the thread from 

 the day of the month over the angular point at XII, and 

 it will cut the sun's declination, as it is north or south, 

 for that day, in the arched scale of north and south 

 declination. 



To find on what days the sun enters the signs : when 

 the bead, as above rectified, moves along any of the 

 curve lines which have the signs of the zodiac marked 

 upon them, the sun enters those signs on the days 

 pointed out by the thread in the scale of months. 



The construction of this dial is very easy, especially 

 if the reader compares it all along with Fig. 3. as he 

 reads the following explanation of that figure. 



Draw the occult line A 73 (fig. 3, plate 6.) parallel to 

 the top of the card, and cross it at right angles with the 

 six o'clock line E C D; then upon C, as a center, with 



