196 Table for ascertaining the Heights of [APRIL, 
With this formula I had constructed a table from 214° to 180°, when 
I perceived that the calculated pressures gradually gained upon the ex- 
perimental ones within the same range, until at 180°, the difference was 
a full third of an inch. This will be seen in the diagram of Plate VIII, 
and in the following comparative table : 
Temperature Calculated Tension Observed Differences Observer 
by Tredgold’s formula Tension 
e in, in. 
212 30.00 30.00 5 assumed 
210 28.86 28.88 + .02 Ure 
210 28.86 28.82 —.04 Robison 
202 24.68 24.37 —.31 Wollaston 
200.75 24.07 24,00 ~- —.07 Dalton 
200 vari | 23.60 —.11 Ure 
200 23.71 22.86 —.85 Robison 
190 19.50%) - 19.00 —.35 Ure 
189.5 19.15 18.80 —.35 Dalton 
182 16.35 16.01 —.34 Southern 
180 15.67 15.16 —.51 Ure 
180 15.67 14.73 ? —.94 Watt 
178.25 15.10 14.60 —.50 Dalton 
173 13.46 13.18 —.28 Dalton 
172 13,17 £2:72 —.45 Southern 
Ropison’s numbers are much too low: the others, DaLTon’s, Soutn- 
ERN’s,and Urg’s, agree pretty well together, gradually separating from 
the curve of Trepeoip’s formula. On the supposition that the experi- 
mental results, when they evince so much regularity, are more trust- 
worthy than the calculus, (which is indeed empirically formed to suit 
them), I have made a deduction of [0.01 inch X number of degrees be- 
low 212], from the numbers in TrepeoLtp’s column, and then I find that 
the experimental and theoretical curves coincide very well throughout 
the range required for our purpose. 
The extreme difference at 180° will thus amount to 
inches. 
LOR NG Weal Phas. Oe aes 15,67 = 1.19511 
hag Of ira te aR EP A, PERS 15,31 = 1.18611 
-00900 
=90 fathoms or 540 feet, a quantity of too much magnitude to be 
passed over. 
Having thus explained the construction of the following Table, I 
will proceed to make a few remarks on the mode of using the instru- 
ment to which it applies. 
