daily variation of the horizontal and dipping needles , &c. 329 
ous and minute peculiarities, which, with his other experi- 
ments, will, I hope, accompany this Memoir. 
Account of the observations made on the daily variation of the 
horizontal needle in various directions. 
My first experiments, as I have already stated, were only 
matters of trial, from which I had merely ascertained that the 
idea I had formed was practicable, and that in certain situa- 
tions the needle had certain directions of motion, but I had 
obtained no numerical results. Having, however, provided 
myself with a needle proper for the purpose, very delicate 
and light, and eight inches and a half in length, I began, to- 
wards the end of March, to register the amount of the daily 
change at every hour, or half hour, from morning to night ; 
my son taking the observations during my occasional ab- 
sence. 
My first observation in the new series was made with the 
north end of the needle pointing to the west, balanced in that 
position with two magnets placed to the southward attracting 
each extremity ; the directive power was considerably re- 
duced, and I obtained a maximum deviation of 3 0 if ; which 
happened at about eleven o’clock in the forenoon, and from 
which time the variation decreased to a late hour in the 
evening. The needle was kept in this position for three 
days, with some change of directive power, but the character 
of the results, as to the direction of motion, the times of com- 
mencement and maximum, &c. were of precisely the same 
nature, but the amount was more or less, according to the 
directive power left upon the needle. 
Having, however, after a few days removed my apparatus 
MDCCCXXIII, U U 
