[ 322 ] 
* 
ftrtaient is g'~ too great, fo that the mean variation is- 
really only 22° n'; and, therefore, as the variation at 
the Society’s Houfe teems to be 1 5 7 greater than it ought 
to be, by reafon of the magnetifm of the building (vide 
the fame place) the true variation feems to be 2 1° 557. 
The reafon why the inftrument now fhews the varia- 
tion 9 7 too great, whereas before the errors was infen- 
tibls is, that a fmall alteration has been made in the 
agate cap of the needle fince the laft year’s obfervations, 
as it was thought not to have been fattened before in a 
fufficiently fteady manner. 
DIPPING 
