WORKS ON THE GEOLOGY AND PALEONTOLOGY OF OXFORDSHIRE, ETC, 327- 



From these results we see tliat the effect of non-clearance of daily 

 means may be quite sensible, although not important. The elliptic 

 monthly tide suffers most, as it did in the results given in Table V., and 

 it seems to follow, from the nature of the mistake which has been made 

 in the reductions, that the values of the elliptic monthly tide assigned in 

 the various reports may be quite sensibly in error. 



It appears from Mr. Roberts' letter in answer to Professor Adams, 

 that the purification of diurnal means has been correctly carried out as 

 regards the diurnal tides, but incorrectly as regards the semidiurnal. 

 In fact, if n be the speed per hour of a semidiurnal tide, sin 12 n/sin ^ n 

 has the opposite sign from sin 67i/sin ^n (which is the factor which has 

 actually been used), and therefore the corrections arising from the semi- 

 diurnal tides have been applied with the wrong signs. 



We may conclude from the preceding discussion that the values 

 deduced for the fortnightly, semiannual, and annual tides are not 

 seriously vitiated ; those for the monthly elliptic tide may be sensibly 

 affected ; and that for the synodic fortnightly is utterly worthless. 



Although I have not seen the actual computations for reducing the 

 long tides, yet it apjDears certain that the process of clearing the diurnal 

 means must be very laborious. The preceding analysis shows that it is 

 perfectly practicable to work with uncleared daily means up to the last 

 stage, in which the final equations for the yl's and i?'s are formed, and 

 the proper corrections may be then applied. The numerical coefficients 



i_ sin I2n sinl82^()/ + A) ^^^ _i_ sin 12?^ sin 1821(r - \ ) 

 "* tan^n sin ^(i' + X) "* tan^n sin-|(»' — X.) 



may be computed once for all, for the influence of each short tide on each 

 long tide. 



Then i (- + 182) — £ is the phase of the short tide at midnight, July 

 1—2, and if time is measured from noon or 0^'' of January 1, r is -^ and 

 X X 182^ may be computed once for all for each long tide. 



Thus the greater part of the materials for the corrections may be kept 

 ready to hand, and the corrections from even four of five tides may be 

 applied very quickly. 



The practical recommendation for future operations which I have to 

 make is, that the clearance should not be effected for each day's mean, 

 but only in the final equations. 



List of Woo'ks on the Geology and Palmontology of Oxfordshire, 

 of Berkshire, and of BucJcinghamshire. By William Whitaker 

 B.A., F.G.S. 



[A communication ordered by the General Committee to be printed in extenso 



among the Reports.] 



1. PREFATORY NOTE. 



This is a continuation of the County or District Lists, of which a 

 Catalogue was given at the head of the Welsh List in the Report for 

 1880 (p. 397). The only additions since made (except the reprints of 



