374 Prof. G. H. Darwin. On an Apparatus for [Dec. 15, 



Number of the last day to be included in the evaluation of the several 

 tides for observations extending over any period up to a year. 



ForM 2 ,)u,2SM,MS. For O. For N, L J, Q. Forv. 



Stop with one Stop with one Stop with one btop with one 

 of the following of the following of the following of the following 



days days days 



(semi-lunations), (semi-lunar periods), (anom. periods). 



days 

 (periods 



or 2??)). 



31 

 63 



222 + 25 

 + 53 



296 + 21 



+ 53 



we erase by proper rules 45 daily sums out of 369, we are left with 

 324, which may be written consecutively in a schedule of 12 columns 

 and 27 rows, of which each corresponds to a semi-lunar period. The 

 summing and analysis is the same as in the last case, but the final 

 division is by 24 times 27, or by 648. 



