meafuring Heights with the Bafmieter. 66 x 
in the cold area underneath, the rate of expan fion for 
the firft io° exceeded that formerly found nearly in 
-the proportion of three to two, while that for the fecond 
and third terms, of io° each, diminifhed progreflively. 
The chief, though not the only caufe of this great 
difference, as will appear hereafter, arofe from the peti- 
tion of the ball of the thermometer, originally inclofecl 
within the wood-work of the frame, which prevented it 
from receiving the heat fo readily as the quickfilver in; 
the tube ; at the fame time that it retained it longer, and; 
confequently produced refults in fome degree fallacious.. 
Finding, from the firft clafs of experiments, that much; 
uncertainty remained with regard to the rate of expan- 
fion of quickfilver affedted by thefe fmaller degrees of" 
heat, and that it was utterly impoffible, from them, to. 
determine its maximum for the i8o° between freezing 
and boiling; I refolved to try, .how much a column of 30 
inches of quickfilver, carefully boiled in a tube, would, 
lengthen, the fame being placed with the open end rip- 
wards in a tin veifel, occafionally filled with pounded ice. 
and water, and afterwards brought to boil, by means of a 
charcoal fire placed underneath ? In this fecond clafs, it 
was eafy to fee, that the expan fion of the tube containing 
the quickfilver,. was neceffarily to be taken into the ac- 
count, and added to that apparently found by experi- 
•2 menh. 
