Pearson — On Comptitafion of Tides. 



659 



Thus, if we take the Liiuar and Solar Tide which is connected with 

 that transit of the moon, which occurs in May, at between 6h. and7h., 

 Greenwich apparent time, and compare theory with observation during 

 the last seven years, we find as follows : — 



Years. 



Moon's 

 Trans. 



Moon's 

 Par. 



Moon's 



Dec. 



S. asc. 



Calculation. 



Observation. 



Error. 

















h. m. 



/ 



„ / 



ft. in. 



ft. in. 



in. 



1876. 



6 31 



55-27 



14-17 



20 9 



20 3 



-6 



1877. 



6 33 



54-16 



16-53 



20 2 1 



20 2 







1878. 



6 41 



54-13 



5-27 



21 1 i 



21 



- 1 



1879. 



6 45 



55-38 



8-45 



21 5 j 



21 2 



- 3 



1880. 



6 25 



58- 4 



13-44 



22 2 I 



22 2 







1881. 



6 17 



58-52 



6-14 



23 3 ' 



23 2 



- 1 



1882. 



6 25 



59-16 



8-52 



23 1 



I 



23 







The above are favourable specimens : all others are not equally so. 

 We shall next examine the atmospheric conditions which seem to 

 account for the variation. Thus, if we take the Lunar and Solar 

 Tides of August, which are incident to the moon's transit between 

 llh. and noon in the same years, with the atmospheric conditions — 



Vparc! Moon's 

 Years. .^^^^^ 



Moon's 

 Par. 



Moon's 

 Dec. 



N. desc. 



Calcula- 

 tion. 



Obser- 

 vation. 



Baro- 

 meter. 



Wind, &c. 



1876. 



1877. 

 1878. 

 1879. 

 1880. 

 1881. 



11-26 

 11-50 

 11-44 

 11-14 

 11-49 

 11-16 



60-30 17-44 

 61-19 18-27 

 60-44 9-41 

 57-36 15-27 

 55- 6 14-17 

 54- 4 10- 8 



28- 

 28- 3 

 28- 9 

 26- 6 

 25-10 

 25- 5 



27-9 

 28-2 

 28-7 

 26-5 

 25-9 

 25-8 



29-8. 

 29-8. 

 29-7. 

 29-6. 

 29-8. 

 29-3. 



calm. 



N.W., slight. 

 S., slight. 

 N.W., fresh. 

 W., slight. 

 S., strong. 



So long as the atmospheric conditions are not very diverse, it is found 

 that the agreement between theory and observation is very nearly 

 perfect ; the changes in the moon's parallax and declination, each 

 producing their own separate effects with undeviating regularity, but 

 when the atmospheric conditions change the effects become apparent. 

 Thus, for the March Tides, lunar and anti-solar, transits between 4h. 

 and 5h., p.m. 



Years. 



Moon's 

 Trans. 



Moon's 

 Par. 



Moon's 



Dec. 

 S. desc. 



Calcula- 

 tion. 



Obser- 

 vation. 



Baro- 

 meter. 



Wind, &c. 



1877. 

 1878. 

 1879. 

 1880. 

 1881. 

 1882. 



4-46 

 4-12 

 4-31 

 4-35 

 4-39 

 4-52 



56- 2 

 58- 1 

 59-19 

 59-17 

 58-40 

 56-53 



25-34 

 26-37 

 25-15 

 22-55 

 23- 6 

 21- 3 



20-10 

 22- 5 

 22- 7 

 22- 8 

 22- 

 21- 1 



20-7 



22-3 

 23-1 

 23-9 

 22-4 

 21-3 



29-5. 

 29-8. 

 29-7. 

 29-7. 

 29-7. 

 30-5. 



N. 



N. 



S.W. 



W.N.W., strong. 



S.W., fresh. 



W.S.W., fresh. 



