64 



(17.) The Convergency of the meridian is readily found for any given distance 

 from the corresponding inclination, by multiplying the Sine of the inclination by 

 the given distance. 



Thus, for latitude 43, the inclination for one mile is 4S".4G ; the sine of which is 

 .000235. This, multiplied by the number of links in a mile, which = 8000, we have 

 the conyergency for one mile,= 1.88 links. 



Multiplying this by the number of miles in a township,= 36, and we have the 

 convergency for a township = 67.68 links. In this manner were the convergencies 

 of table III computed. 



(18.) Deflection of Range-Lines from meridian. The second column of table III 

 shows the surveyor how much he must deflect the range lines between the several 

 sections of a township from the meridian, in order to make the consecutive ranges 

 of sections in a township of uniform width, for the purpose of throwing the effects 

 of "convergency" into the most westerly rangeof quarter sections agreeably to law. 



Thus, say between 45 and 55 of latitude, the inclination is practically V for 

 every mile of easting or westing. Then, bearing in mind that in the U.S., *V sur- 

 veys arc regarded as projected from the East and South to the West and North ; the 

 surveyor must project theirs* range-line between the sections of a township in those 

 latitudes, 1' to the left of the meridian. 



The second, 2' ; the third, 3' ; and so on to the fifth, which must be 5' to the left 

 of the meridian on the east side of the township. 



By this means all the convergency of the township is thrown into the sixth, or 

 westerly range of sections, as the law directs. 



The fourth- column of the above table shows the amount of this convergency. 

 This column is also useful in sub-dividing a block of territory embraced by two 

 ^taiulard parallels" and two "guide meridians" into townships. Thus, starting a 

 meridian from a standard parallel on latitude 43 N, for the western boundary of 

 a range of township, say the first one west from the guide meridian, and running 

 North, say 4 townships, the surveyor must make a point that is East of the six-mile 

 point on the northern "standard parallel" 4 X 67.7 links = 270.8 links, The second 

 meridian should fall 8 X 67.7 links to the right of the twelve-mile point, etc. 



(19.) The Variation of the Needle. This is easily determined by noting the 

 reading of the needle when the solar transit telescope has been brought into th 

 meridian. 



C. L. Berger & Sons' Solar Attachment for Mining 



Transits. 



This Solar Attachment, designed and patented by the firm, illustrated on page 

 168, consists of an equatorial adapter, an auxiliary telescope, and a striding level. 



The equatorial adapter made to fit to the upright post, on milling transits 

 with style I interchangeable auxiliary telescope, where the auxiliary telescope 

 ordinarily goes, receives the auxiliary telescope and converts it into a solar 

 telescope, permitting it to move in the equatorial circle about a polar axis, 

 and in the declination circle of the sun. The adapter consists of two plates 

 provided with leveling screws working against opposing springs which permit 

 the polar axis to be adjusted to the zenith when the main telescope is level, 

 and consequently to point to the pole when the main telescope is elevated in 

 the plane of the meridian to intersect the equatorial circle. The lower plate of 

 the adapter screws upon the central vertical post of the mining transit which 

 was originally designed to carry the auxiliary telescope -when used as a top 

 telescope. The upper plate of the adapter carries a small level and the socket 

 which moves around the polar axis. This socket carries an arm in which the 

 declination axis can be made to revolve. The declination axis has at one end a 

 threaded stud similar to those provided for the auxiliary telescope when used as 

 a side or top telescope and to which the auxiliary telescope can be screwed. To 

 do this it is only necessary to slightly release the innermost nut from its fasten- 

 ing against the upright and then by turning the declination axis by means of 

 the outer milled-headed screw, the auxiliary, now the solar, telescope can bo 

 securely fastened thereto. 



