xli 
comen’s (atmospheric) engines only remained in the Coutity ;* 
and in 1790 this had disappeared. 
The dues payable to the patentees on engines actually at work) £4 390 
amounted in 1782 to ; 
The dues to which the patentees would become entitled on 9.000 
engines in course of erection, would realize in 1782 \ g 
The dues payable to the patentees on engines already erected, 
would realize in 1784 
ee are aaa } 12,000 
a year.{ Particulars of the performance during fourteen expe- 
riments on nine engines erected in Cornwall, “by Boulton and 
Watt between 1783 and 1792—ranging from 10-1 to 13°3 (per 
bushel or from 13:4 to 41:7 per ewt.) —averaged 22°5 per bushel, 
or 30° per cwt. of coal expended.§ In 1793 seventeen engines, 
which had been set up by Boulton and Watt, performed an aver- 
age duty of lifting one foot 19°5 millions per bushel, or 26° per 
hundred weight “of coal consumed. || In 1798, however, the per- 
formance of “twenty- -three engines ranged from 6° to 29-6, and 
* Smiles, Lives of Boulton and Watt, p. 327. 
+ Farey, Steam-Engine, p. 383. Pole, Cornish Pumping Engine, p. 21. 
t Smiles, Lives of Boulton and Watt, pp. 317, 393. 
Duration of | Diameter of | Dut Dut 
§ Mine, Year. | speriment.| Cylinder. |84lbs/bushel.| owt 
Wheal Virgin, EL 1783 — —= 22,930,414 | 30,573,885 
Poldice, H.....-- os — — 21,304,762 | 28,406,349 
op) |) oBoeon 1784 — a= 21,630,795 | 28,841,060 
Brees iss 1786 — 21,652,429 | 28,869,905 
PARP Neicha'oie' 1792 |4 Months. — _| 26,737,339 | 35,649,785 
Dolcoath ......+.- 1784 — 22,646,554 | 30,195,405 
54 eee 1785 —— — | 22,396,891 | 29,862,571 
TYeSAvedn + .0-+. 28 Days. | 28 inch. | 20,304,265 | 27,072,358 
/Pathfiode sdneeee 1785-1786 | 2 Months. 29,225,750 | 38,967,666 
Ale and Cakes. . 1786 1 Month. —— _/81,338,850| 41,785,133 
Wheal Maid ....| 1789 Nese 26,116,034 | 34,821,378 
3, Se 1790 "s 25,231,695 | 33,642,260 
Wheal Jewell....| 1791 | 8 Days. apes 10,102,269 | 13,469,692 
Seal Hole....... 3 20 inch. | 13,938,986 | 18,585,314 
Witson. A comparative statement of the effects of Messrs. Boulton and 
Watt's Steam- Engines, with Newcommen’s and Mr. Hornblower’s, (Truro, W. 
Harry,) 1792. 
For a sight of this rare and interesting pamphlet I am obliged to Mr. 
F. W. Michell, C.E., 
of Trewirgie, near Redruth; and for the register of the 
author’s burial at Falmouth, on the 4th of July, 1820, at the age of 72, I am 
indebted to Mr. Alfred Fox, of Glen Durgan, near Falmouth. 
|| Gilbert, Pail: Trans: exx., p. 125. 
