138 BEN.T. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



diameter, and their breadth, <fec., proportionable. The out- 

 ward ring represents the meridian of any place you are at, 

 and contains two divisions of 90 each, diametrically oppo- 

 site to one another, serving the one from the equator to the 

 north, the other to the south pole. The inner ring repre- 

 sents the equator, and turns exactly within the outer, by 

 means of two pivots in each ring, at the hour XII. Across 

 the two circles goes a thin reglet or bridge, with a cursor, 

 that slides along the middle of the bridge. In the cursor is 

 a little hole for the sun to shine through. The middle of 

 this bridge is conceived as the axis of the world, and the 

 extremities as the poles ; and on the one side are drawn the 

 signs of the zodiac, and on the other the days of the 

 month. On the edge of the meridian slides a piece, to which 

 is fitted a ring to suspend the instrument by. On the sur- 

 face of the inner ring the hours and parts are engraved. 



To USE THE UNIVERSAL RING DIAL. To find the Sun's 

 Declination and his place in the Ecliptic. Set the slider on 

 the diameter or bridge, to the day of the month, and, answer- 

 ing to it on the other side, is the sun's place and his declina- 

 tion, either north or south, as the letters so marked direct. 



To find the Latitude of the Place. Find the sun's decli- 

 nation for that day ; then, if it be north, set the slider or 

 hanging piece to so many degrees on the front of the dial 

 marked S ; but if it be south declination, set the hanging 

 piece on that side of the graduated circle marked N. Put 

 a pin or wire in the small hole on the back side of the 

 instrument ; hold it up by the ring, the pin towards the 

 sun, so that the shadow thereof falls amongst the divisions 

 on the back of the dial ; then watch for the greatest alti- 

 tude ; which, counted from the lowermost part of those 

 degrees, the shadow so cut will be the latitude required. 



To find the Hour of the Day. Set the slider on the me- 

 ridian to the latitude of the place, and the slider on the 

 bridge or axis to the day of the month ; then open the hour 

 circle (now holding the instrument by the little ring, that 

 it may hang freely), turn the bridge towards the sun, till 

 you can see a small speck of light come through the slider 

 of the bridge, and fall on the middle line of the hour circle ; 

 and that point in the middle line where the speck falls, 

 shows the hour of the day at that place. The instrument 

 hanging in this position, the meridian, equinoctial, poles, 

 axis, <fec., are all of them correspondent to those supposed 

 in the heavens. Price, $6 to $20. 



