Experiments and Qbfervations . 1 7 
Hand farther from the veffel containing the filings, &c. than it 
Hood before the vitriolic acid was added, which diminution of 
attraction is certainly owing to the lofs of phlogifton ; it being 
well known, that iron is lefs and lets attracted by the magnet 
in proportion as it approaches nearer to the calcined Hate. 
Here follows the particular account of the above-mentioned 
experiment. 
The fouth end of the needle coincided with the 285° 15' on 
the divided circle. When the pot with the iron filings was 
placed on one fide of it, the needle pointed to 286° 15'', being 
drawn juH one degree nearer. Having added the diluted vitriolic 
acid to the filings, the needle came nearer, and Hood at 286° 
4^. Ten minutes after the beginning of the effervelcence it 
Hood at 2S6 0 35b having receded a little ; and a few minutes 
after this obfervatioti it Hood at 286° 3c 7 . An additional quan- 
tity of diluted vitriolic acid was now added, which increafed 
the effervelcence confiderably ; and on obfcrving it a fhort time 
after, the needle was found at the fame point at which it Hood 
before, from which time it began to go back very gradually ; l'o 
that about three hours after it Hood at 285 50', viz. farther 
from the effervefcing mixture than it Hood before any vitriolic 
acid was poured upon the iron filings. 
As a fingle experiment ought not to be depended upon when 
an error may be occalioned by many concurring circumflances, 
I repeated this experiment with great precaution, taking care - 
that nothing could lhake the needle, or the ref of the appa- 
ratus ; but the refult was nearly the fame, the attraction be- 
tween the iron filings and the needle being increafed by the 
adion of the vitriolic acid. 
In order to afcertain that, this effed was not owing to the 
heat generated by the effervefcence, the pot, with fome iron 
Vol. LXXVII. D filings, 
