464 On Steam Boilers. 



During the last month (November), accoi'ling to Messrs. Leans' 

 Report, Woolf's engine at Wheal Vor consnined 1 154 bushels 

 of coals, and with each bushel lifted 50,445, liiO jjounds of water 

 one foot high ; and his engine at Wheal Abraham during the 

 same month consumed 1044 bushels of coals, and lifted, with 

 each bushel, 52,o27,4000 pounds, one foot high. 



LXXXVI. On Boilers employed to produce Steam of High 

 Pressure. By T. Gill, Esq. one of the Cliainnen of the 

 Soc'itly for the Encouragement of Arts, Manvfactures and 

 Commerce. 



To Mr. Tilloch. 



SiK, — 1 WAS much pleased with the judicious remarks con- 

 tained in vourlast number, on the lamentable accident in Well- 

 street, Goodman's Fields, occasioned by exposing a close boiler 

 to so high a temperature as to cause an explosion attended with 

 and followed by such fatal consequences. If the makers of 

 boilers that are to be employed in producing steam of high pres- 

 sure do not adopt those precautions which sliall preclude the 

 possibility of such accidents, they will deter all prudent people 

 from the use of this invaluable agent. Already this has been the 

 case with respect to the use of loco-motive engines on some of 

 the rail-ways, in consequence of the exj/losion of that at New- 

 bottle Colliery, alluded to in your last nimiber, and which was 

 occasioned by a culpable obstinacy which caused the death of 

 the engineer and several other people. Some years ago, when 

 a, high pressure engine near Woolwich ^vas burst by the steam, 

 the miscliief was owing to similar madness — the ivilfd ob- 

 struction of the safety valve to prevent the possibility of steam 

 escaping ! After the last-menlioned accident, several effectual 

 means to prevent such accidents were contrived by IMr. Trevi- 

 thick (who first brought the higli-prcssure engines into use). In 

 the first place, lie jiroposed inclosing the safety-valce in such a 

 manner that no one could get access to it to increase the load 

 beyond that intended ; and secondly, in addition to the recurved 

 tube with mercury (which can be adjusted with precision to any 

 pressure intended to be employed, and will blow out before the 

 Rieam, when the pressure rises even a single pound higher) he 

 drilled a hole in tlie bnilcf , which he i)luggcd up with lead, at 

 such a height from the bottom, that the boiler could never boil 

 dry without cx])osing the lead to be melted; and consequently, 

 making an opening for the steam, which by its escape into the 

 fire extinguishes it. This coutrivaace is calculated to prevent 



the 



