39J. 



KEroRT — 1872. 



crements (p. 361), and these adcKtions may be continued for any period 

 whatever. These are most readily obtained by the use of the arithmometer 

 of Thomas (de Cohnar). 



The residual differences, on this and the following page, arc for the most 

 part negative, and indicate that the mean height of the water on the day in 

 question was above the mean height of the water for the whole year. On 

 trial it will be found that the excess equals 0-15 of a foot, a quantity such 

 that, if applied to the residual differences, will make them all very small. 



