316 TUBULAR BOILER, SUPERHEATING STEAM, 



have been made ; and to prove this they left out the fires in 

 the flues, and the engines fell back to their former duty, and 

 the condensing water increased in the same proportion. 



" The surface sides heated by this 5 bushels of coal is about 

 300 surface feet, the saving effected is 1781 millions, which is 

 six millions saving for each foot of surface on the castings in the 

 flues. In Wheal Towan engine that did eighty-seven millions, 

 the surface sides of the boiler was 1000 feet of fire-sides for every 

 bushel of coal burnt in an hour, and the duty performed per 

 minute from each foot of boiler fire-sides was 1500 Ibs. 1 foot high. 

 Now it appears that the heating of Binner Downs 300 surface 

 feet gave a saving of 6000 Ibs. per minute per surface foot ; 

 whereas the boiler sides only gave 1500 Ibs. of duty per minute 

 for each foot of boiler " fire-sides. Therefore the saving by 

 heating the sides of the cylinder is equal to four times the duty 

 done by each square foot of boiler sides ; and further, it appears 

 that the 300 feet, when not heated, though clothed round with 

 brickwork, condensed or prevented from expanding the steam 

 of 41 bushels of coals, which was eight times as much steam 

 condensed as the 5 bushels of coal would raise. Now if this be 

 a report of facts, which I have no reason to doubt (but still I 

 will be an eye-witness to it next week), there must be an 

 unknown propensity in steam above atmosphere strong to a 

 very sudden condensation, and vice versa, to also a sudden 

 expansion, by a small heat applied to the steam-sides ; and if 

 by heating steam, independent of water, such a rapid expansion 

 takes place, certainly a rapid condensation must tnke place in 

 the same ratio, which might be done at sea by cold sides to a 

 great advantage, always working with fresh water. 



" I shall have a small portable engine finished here next 

 week, and will try to heat steam, independent of water, in small 

 tubes of iron, on its passage from the boiler to the cylinder, and 

 also try cold sides for condensing. 



" If the above statement prove to be correct, almost anything 

 might be done by steam, because then additional water would 

 not be wanted for portable engines, but partially condensed and 

 again returned into the boiler, without any fresh supply or the 

 incumbrance of a great quantity ; and boilers might be made 



