SErTElIBER, 1903.] 



KNOWLEDGE 



205 



latituile of Europe, ainl give lari^-o eclipses over approxi- 

 uuLtelv the same regions. As examples, may be given 1715, 

 \7-2-l 'ihoih total in England); 1887, 1896 (Siberia and 

 Japan) ; 191:5, 1954 (Norway), etc., etc. This is not suffi- 

 ciently regular to be called a law, but it is worth while 

 seeking in any European totality, whether there is another 

 one nine years l)efore or after. 



It may be remarked that Mr. Maunder has considerably 

 under-estimated the possible career of an eclipse in the Sar. 

 He gives it as 71 returns, but according to Oppolzer it 

 may reach 85 (as in the case of an eclipse that died in 

 A.D. 670) ; there ai-e seven cases of 80 returns or upwards 

 in the Canon. 



time. 1902 had three partial solar eelijises. Then follow 

 a group of si,\ central eclipses (two each in 1903,-4,-5). 

 This year's eclipses are in their decrepitude, and end their 

 career as central eclipses in 1957 and 1939 respectively. 

 Next year's eclipses are in full vigour, while those of 1905 

 are in comparative youth and began their central career in 

 1598, 1797 respectively. 



The Sar. may be used to give, without calculation, a 

 rough position of the moon at any time in a year for which 

 no Almanac is available. Thus, suppose we desire to 

 obtain a rough place of the moon at 11 p.m. on March 21, 

 1921. We take from the Almanac its place one Sar. earlier. 



[Note that the Sar. consists of 18'' 12i'' when three 29ths 



Plate II. — Diagram illustrating the past history of the Eclipses of 1S68 and 1927 in the 521-Tear Cycle 



The following is an easy way of diagnosing the approxi- 

 niate age of a central eclipse in the Sar. 



A glance at Oppolzer will show that wo have generally 

 a group of partial eclipses (2, 3, or 4), followed by a group 

 of central eclipses (4. 5, or 0), of course separated from 

 one another by six months. Then wo can infer that the 

 central eclipses at the beginning of such a group are in 

 their decrepitude, those in the middle of tbi> group are in 

 their full vigour, while those at the end of it have just 

 began their central career. In a word wt' may apply the 

 adage " Seniores priores '' to the group, which is often a 

 useful aiil to the memory. 



As an example wo may take (he eclipses of the present 



of February are included in the interval, 18' 11^'' when 

 four are included, 18'' 10^'' when five are included.] 



In this case five 29ths of February are included, hence 

 the corresponding date is 1903, March 11' 3 p.m. 



We take from the Almanac the age of the moon at this 

 time, viz., 122 days ; this will also be its age at the epoch 

 required in 1921. 



We also take its R.A. and Dec, viz.. R.A. 0'' 42"' 4, 

 N. Dec. 92^ 27', insert this tm a star map, and then shift 

 it eastward 10""8 parallel to the echptic. The result is a 

 close approximation to the place of the moon at the time 

 named ; iu this case we obtain 10'' 20° 'l. N. Dec. {)° 3'. 



As another example, the age of the moon at noon, 



