wa ESSAYS asp OBSERVATIONS 
advantage too in ufing a plain furface of 
foap water, that, before it freezes, the 
obferver may draw out any particular 
colour or feries of colours, which he chu- 
des, to a greater breadth, by ftroaking it 
‘along with a wet finger. For this reafon, 
amoneg{t others, I have found it a more 
convenient fubject for examining the va= 
rious orders of colours, than {phericat 
bubbles adhering to a plane. Perhaps, 
melted refin might be drawn out into a 
thin-celoured plate before it hardens ; for 
I have often blown it into bubbles with 
a tobacco-pipe till it became coloured. f 
Know no other ways in which the various: 
orders of colours can be preferved for de- 
liberate inf{pection, but either in a frozen 
plate of water or rofin, or in the perma= 
nent /coria that appear on heated metals. 
I have counted, on the fide of a clean 
polifhed copper tea-kettle, the fix firft or- 
ders of colours diftintly and regularly 
ranged in ‘the fame fucceffion in which 
they appear in the foap-bubbles; the firit 
order being formed on that part of the 
kettle that had been Icaft heated. 
Qr Er. 
