( 733 ) 
and consequently ehanges the octant pairs (1,2) and (7,8) resp. for 
(3,4) and (5,6). 
The diagrams of which I have served myself for the graphical 
solution of the problems discussed above, and which will be published 
: : 8 Ld 
elsewhere, give for angles « varying between 0 and + 5 and pro- 
bed 
gressing with 10°, the values of / for secant planes, of which azimuth 
and height of poles, likewise progressing with 10°, vary between 
JT 
gb and 22,16 = (land = st 
2 
any indifferent secant plane can be found from it for every value 
of @ with sufficient accuracy. 
The way in which the problem must be solved may be explained 
to two of the problems treated analytically above. If one con- 
siders fig. I, then it is clear, that by a graphical treatment one 
can finder A OB ht in the; diagram for «= @, i. e. with 
Bs Be: im the same way AOB —h, in the 
diagram for « =a, with 0, = ~ C, BQ = o0—y and o= PQ. 
If on the contrary one wishes to determine from the given angles 
a@,, h,, and a,, h, the locus of the secant plane P (9,5), then the 
diagrams for @, and «‚ must be laid on each other, the latter with 
regard to the former turned over an angle — y, and one must 
By interpolation the value of / for 
1) 
