C. 34-7 ] 
Power in the heated fupporting Tubes, when placed 
near together, might poffibly be the Occafion of 
the receding of the upper Tube at Contaft with them. 
To put the Matter out of all Doubt, Lwet the three 
Tubes all over; yet the regrefiive and rotatory Mo- 
tion was (till manifeft, with very little, if any Differ- 
ence; not more than might be well accounted for, 
from the Increafe of Refinance by Wetting. 
Thefe two Experiments fully convinced me, that 
neither Attraction nor Repulfion would be of any 
Affidance in folving our Rotation, Upon confider- 
ing therefore the Matter farther, 1 found nothing was 
wanting, but that the moving Tube fhould fvvell to- 
wards the Fire and indeed 1 thought I could per- 
ceive fuch a Swelling in Mr. Or me s long Tube of 
four Feet and an half, which I faw firft placed near 
a good Fire in the Manner deferibed in my laid. For, 
allowing fuch a Swelling, Gravity mud pull the Tube 
down, when fupported near its Extremities horizon- 
tally ; and a frelh Part being expofed to the Fire, and 
fwelling out again, muft fall down again, and fo on 
fucceffively ; which is, in other Words, a rotatory 
Motion towards the Fire. 
When the fupporting Tubes are brought near to 
each other, as well as near to the Centre of the fup- 
ported Tube, then the Parts hanging over on each 
Side, being larger thanjj the Part which lies between 
the Supporters, will, by their Weight, pull down- 
wards, and confequently force the middle Part, refl- 
ing upon its two Fulcra , upwards ; and being left 
advanced towards the Fire, as being lefs heated, will, 
by their oblique Situation, pull the middle Part back- 
j ward alfo from the Fire : Which Effebls, being fuc- 
cellive. 
1 
