THE WATT AND THE TREVITHICK ENGINES. 125 



trig irom the valve. He was hurt, but is now recovering ; he 

 had left the engine about an hour. I would be much obliged 

 to you if you would calculate the pressure required to burst this 

 boiler at 1 inch thick, supposing it to be a sound casting, and 

 what pressure it would require to throw the materials the dis- 

 tance I have before stated, for Boulton and Watt have sent a 

 letter to a gentleman of this place, who is about to erect some 

 of those engines, saying that they knew the effects of strong 

 steam long since, and should have erected them, but knew the 

 risk was too great to be left to careless enginemen, and that it 

 was an invention of Mr. Watt, and the patent was not worth 

 anything. This letter has much encouraged the gentlemen of 

 this neighbourhood respecting its utility ; and as to the risk 

 of bursting, they say it can be made quite secure. I believe 

 that Messrs. Boulton and Watt are about to do me every injury 

 in their power, for they have done their utmost to report the 

 explosion, both in the newspapers and in private letters, very 

 different to what it really was ; they also state that driving a 

 carriage was their invention; that their agent, Murdoch, had 

 made one in Cornwall and shown it to Captain Andrew Vivian, 

 from which i have been enabled to do what I have done. I 

 would thank you for any information that you might have 

 collected from Boulton and Watt, or from any of their agents, 

 respecting their even working with strong steam, and if 

 Mr. Watt has ever stated in any of his publications the effects 

 of it, because if he condemns it in any of his writings, it will 

 clearly show from that, that he did not know the use of it. 

 Mr. Homfray, of this place, has taken me by the hand, and will 

 carry both the engines and the patent to the test. There are 

 several of Boulton and Watt's engines being taken down here, 

 and the new engines being erected in their place. Above 700 

 horse-powers have been ordered at 12?. 12s. for each horse-power 

 for the patent right, and the persons that ordered them make 

 them themselves, without any expense to me whatever. If I 

 can be left quiet a short time I shall do well, for the engines 

 will far exceed those of Boulton and Watt. The engine at 

 Greenwich did fourteen millions with a bushel of coals ; it was 

 only an 8-inch cylinder, and worked without an expansive cock, 



