[ 4°4 ] 
negative j this will likewife be the cafe when it is 
taken out of boiling water, and fuffered to cool ; but 
the fide that was pofitive while it was heating, will 
be negative while it is cooling, and the fide that was 
negative, will be pofitive *, 
For the fake of thofe who may be defirous of ex- 
amining the diurnal variations of the needle very 
minutely, I (hall annex a complete years obferva- 
tions i and fhall deduce, from the regular variations 
during that time, the mean diurnal variation belong- 
ing to each month : whence it will appear, that the 
diurnal variation increafes from January to June, and 
decreafes from June to December. 
In the following table, the firft column contains 
the day of the month j and the fecond, the hour and 
minute of the day (according to equal time), when 
each obfervation was made. The third column con- 
tains the abfolute variation of the needle weflward, or 
the angle it made with a true meridian line at the re- 
fpedtive times j which differs lefs than two minutes 
of a degree from that at Greenwich, where the reve- 
rend Dr. Bradley was fo kind as to give me feveral 
opportunities of taking it, in his prefence, by the cu- 
rious apparatus for that purpofe, belonging to the 
royal obfervatory. And in the fourth column are fet 
down the degrees of heat, by a Fahrenheit’s thermo- 
meter, hung without, in the fhaded air, on the north 
fide of the houfe. 
* See the Gentleman’s Magazine for laft September. 
Spital 
