SCIENCE ABSOLUTE OF SPACE. 



13 



same; and every ray BN is also axis of L, and 

 between all axes of this L, is . 



The same is evident in the same way of F. 

 13. If BN II AM, and CP II DQ, andZBAM 

 +ZABN=st.Z; then also ZDCP+ZCDQ= 

 st.Z. 



Q For let EA= 

 EB, and EFM= 

 DCP ( 4). Since 

 ZBAM+ZABN 



SN 



S O 



I 



=st. Z = 

 ZABG, we have 



FIG. 11. 



D and so if also BG 

 =AF, thenAEBG 



\ ZBEG-ZAEF and G will fall on 

 the ray FE. Moreover ZGFM+ZFGN=st. Z 

 (since ZEGB=ZEFA). 

 AlsoGNllFM (6). 



Therefore if MFRS^PCDQ, then RSllGN 

 ( 7), and R falls within or without the sect 

 FG (unless sect CD = sect FG, where the thing 

 now is evident). 



I. In the first case ZFRS is not >(st.Z-Z 

 RFM=ZFGN), since RSllFM. But as RSl'l 

 GN, also ZFRS is not <-ZFGN; and so ZFRS 

 and ZRFM+ZFRS=ZGFM+Z 



