7 
DIRECTIONS FOR PLOTTING THE PROJECTION 
{See Figure 3) 
In the middle of a sheet of paper of determined size according to the 
scale of the map, draw a vertical line to represent the central meridian of 
the projection — longitude 95 degrees west — and the axis of ordinates. 
Midway on this median line, mark the intersection of the parallel of 60 
degrees and, through this point as origin of co-ordinates, draw a perpen- 
dicular across the sheet to represent the axis of abscissae. From the 
origin, scale in the usual manner, the co-ordinates x and y of the inter- 
sections of meridians and parallels taken from the tables : abscissae are 
plotted on both sides of the central meridian, and the ordinates above or 
below the axis of abscissae according to the sign -f- or — preceding the y 
values. The plotted intersections are then joined by suitable curves 
representing meridians and parallels. Should a network of 1-degree 
quadrilaterals be desired, graticulation may be completed by subdividing 
the 5-degree quadrilaterals by means of the scale or proportional divider. 
The parallels should be subdivided in equal parts, and the meridians in 
the ratio of meridional distances given in Table I. 
Table I 
Latitude 
Number 
of degrees 
in arc=n 
Meridional 
distance 
— M-n or Ma 
Log radius 
of spherical 
zone = log 7 
r in 
statute 
miles 
60“ to 40“ 
20 
Miles 
-1,382-282 
3-5976892 
3,959-945 
60“ to 41“ 
19 
-1,313-282 
3-5977263 
3,960-284 
60“ to 42“ 
18 
-1,244-270 
3-5977646 
3,960-633 
60“ to 43“ 
17 
-1,175-246 
3-5978023 
3,960-977 
60“ to 44“ 
16 
-1,106-210 
3-5978400 
3,961-321 
60“ to 45“ 
15 
-1,037-162 
3-5978777 
3,961-665 
60“ to 46“ 
14 
- 968-102 
3-5979152 
3,962-006 
60“ to 47“ 
13 
- 899-029 
3-5979525 
3,962-346 
60“ to 48“ 
12 
- 829-944 
3 -.5979901 
3,962-690 
60“ to 49“ 
11 
- 760-847 
3-5980272 
3,963-028 
60“ to 50“ 
10 
- 691-738 
3-5980642 
3,963-306 
60“ to 51“ 
9 
- 622-617 
3-5981012 
3,962-704 
60“ to 52“ 
8 
- 553-484 
3-5981377 
3,964-0.37 
60“ to 53“ 
7 
- 484-339 
3-5981740 
3,964-368 
60“ to 54“ 
6 
- 415-182 
3-5982090 
3,964-695 
60“ to 55“ 
5 
- 346-018 
3-59824.50 
3,965-016 
60“ to 50“ 
4 
- 276-833 
3-5982802 
3,965-337 
60“ to 57“ 
3 
- 207-642 
3-5983165 
3,965-669 
60“ to 58“ 
2 
- 138-439 
3 -.598.3511 
3,965-985 
60“ to 59“ 
1 
- 69-225 
3-59838.56 
3,966-300 
60“ to 60“ 
0 
0 000 
3 -.5984 195 
3,966-615* 
60“ to 61“ 
1 
+ 69-236 
3-5984.546 
3,966-930 
60“ to 62“ 
2 
+ 138-482 
3-5984859 
3,967-218 
60“ to 63“ 
3 
+ 207-738 
3-5985173 
3,967-504 
60“ to 04“ 
4 
+ 277-004 
3-5985486 
3,967-789 
60“ to 65“ 
5 
+ 346-280 
3-5985800 
3,968-075 
60“ to 66“ 
6 
+ 415-566 
3-5986114 
3,968-363 
60“ to 67“ 
7 
+ 484-861 
3-5986430 
3,968-648 
60“ to 68“ 
8 
+ 554-165 
3 -.5986716 
3,968-913 
60“ to 69“ 
9 
+ 623-477 
3-5987004 
3,969-176 
60“ to 70“ 
10 
+ 692-797 
3 -.5987286 
3,969-434 
60“ to 71“ 
11 
+ 762-125 
3-5987562 
3,969-686 
60“ to 72“ 
12 
+ 831-461 
3-5987831 
3,969-932 
* This value of t is the length of the meridian radius of curvature of the earth at latitude 60 
degrees converted into miles from the Smithsonian Geographical Tables. 
