[ 45 ° ] 
After this, I contrived to take with me, whenever 
I went into the country, a little oil in the upper hol- 
low joint of my bamboo cane, with which I might 
repeat the experiment as opportunity fhould offer j 
and I found it conifantly to lucceed. 
In thefe experiments, one circumflance ftruck me 
with particular furprize. This was the fudden, wide, 
and forcible fpreading of a drop of oil on the face of 
the water, which I do not know that any body has 
hitherto confidered.. If a drop of oil is put on a 
polifhed marble table, or on a looking-glals that lies 
horizontally ; the drop remains in its place, fpread- 
ing very little. But when put on water it lpreads 
ioifamly many feet round, becoming fo thin as to 
produce the prifmatic colours, for a conliderable fpace, 
and beyond them fo much thinner as to be invilibie, 
except in its effect of fmoothing the waves at a much 
greater diflance. It feems as if a mutual rep.ulfion 
between its particles took place as foon as it touched 
the water, and a repuliion lo ftrong as to aft on other 
bodies fwimming on the furface,. as draws, leaves, 
chips, &c. forcing them to recede every way from 
the drop, as from 'a center, leaving a large clear fpace. 
The quantity of this force, and the diflance to which 
it will operate, I have not yet afeertained ; but I think 
it a curious enquiry, and I wifh to underhand whence 
it ariles. 
In our journey to the north, when we had the plea- 
fure of feeing you at Ormathwaite, we vifited the cele- 
brated Mr. smeaton near Leeds. Being about to 
fhew him the fmoothing experiment on a little pond 
near his houfe, an ingenious pupil of his, Mr. JefTop, 
then prefent, told us of an odd appearance on that pond, 
2 which 
