Description of the Solar Index. 307 
Size of the several parts of the Instrument. 
Length of the horizontal axis B, : ; - 31 inches. 
Diameter of the square part of this axis, . 5 ee 
Height of this axis above the base A, ‘ ee 
Length of the tube E, ae the diameter 2 the 
axis, 4 : ‘ ae 
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Width of the eles Cad D, ilies 
Thickness of these and of the base A, 
Radius of the quadrant, (to the middle of the Fa eee 
Breadth of the limb, : ‘ 
Breadth of the radii G and I at ihe ira 
ee i a at the centre, 3" 
Thickness of the quadrant, 
Focal length of the lens, 
Diameter of the lens, 
Distance of the lens ane the baie 33 the rears 
Width of the bar K, E ; 5 ; ; 
Diameter of its pivot, ‘ 
The arm LM of the same ae sar the tae K, 
where it branches from it; but narrows a lit- 
tle toward the vernier. 
The vernier in my instrument is of silver, and sol- 
dered firmly upon the extremity of the arm 
LM, which is shaped so as to receive it. 
Thickness of the bar K and of the arm LM, a trifle 
less than i : , aoe 
Length of the spirit level rare the st, é Pes sauce 
Diameter of the cylindrical portion of the corenral 
axisvat QQ)... : ; , 3 . SEP 
Diameter of dov at R, . : See 
That portion of this axis which receives ie ecea is} an 
inch wide at the centre of the quadrant, and , of an inch et Q. 
It is first made 7, of aninch thick, and receives the quadrant im- 
bedded into one side of it about #7, of an inch; it is then filed 
off on the opposite side till it is left about 2, of an inch thick. 
These dimensions afford an instrument of very proper and 
convenient size; which will be found of easy construction, and 
little liable to get out of order. It can be snugly packed ina 
box about half the size required for the compass,—the equatorial 
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