HEATING APPARATUS. 365 



table, would by being drawn up or down adjust the required 

 heat and hide the boiler, and would be warm and comfortable 

 to sit at. I think this plan would save three-quarters of the 

 coal at present consumed; the expense of the boiler will not 

 exceed 5. When you have taken it into consideration, please 

 to write me your opinion. 



" I remain, Sir, 



" Your very humble servant, 



"ED. TREVITHICK. 



" P.S. Boiler, 3 feet diameter, 3 feet long ; fire-tube, 12 inches 

 diameter, placed in the boiler, the same as my old boilers, made 

 of iron plates |th of an inch thick, weighing about 2 cwt. 



"I had a summons to attend at Guildhall last Saturday on 

 the coal trade, and was requested to attend a committee at 

 Westminster for the same purpose, in consequence of my apply- 

 ing small engines to discharge ships. 



" I attended, but with difficulty, from my ill-health." 



Trevithick was not above scheming for his friend's 

 hot-house, warming it by a boiler on wheels, in form 

 like his high-pressure steam-boiler. Booms had before 

 been beated by steam or bot air in pipes ; but be 

 tbougbt a more simple and economical plan was to 

 heat a certain quantity of water to boiling beat at any 

 convenient place baving a chimney, or in tbe open air, 

 and tben wheel the apparatus into tbe room to be 

 warmed. If tbe room bad a chimney, tbe fire could be 

 kept up, or the temporary iron connecting chimney 

 be removed and the apparatus wheeled into the middle 

 of the room and used as a table. 



The scheme promised to be successful, for in a letter 

 nine months after the former he wrote that he had 

 taken a patent for France, where it had made a great 

 bustle among the scientific class, for coal in Paris was 

 '3s. a hundredweight ; some hot -water room -heaters 



