The engine was to work two hammers, but was capable of working four of 7 cwt. each. He says, with excusable pride,
I believe it is a thing never done before, to make a hammer of that weight make 300 blows per minute; and, in fact, it is more a matter to brag of than for any other use, as the rate wanted is from 90 to 100 blows, being as quick as the workmen can manage the iron under it.
This most ingenious application of steam power was included in Watt's next patent of April 28, 1784. It embraced many improvements, mostly, however, now of little consequence, the most celebrated being "parallel motion," of which Watt was prouder than any other of his triumphs. He writes to his son, November, 1808, twenty-four years after it was invented (1784):
Though I am not over anxious after fame, yet I am more proud of the parallel motion than of any other mechanical invention I have ever made.
He wrote Boulton, in June, 1784:
I have started a new hare. I have got a glimpse of a method of causing a piston-rod to move up and down perpendicularly, by only fixing it to a piece of iron upon the beam ... I think it one of the most ingenious simple pieces of mechanism I have contrived.
October, 1784, he writes:
The new central perpendicular motion answers beyond expectation, and does not make the shadow of a noise.
He says:
When I saw it in movement, it afforded me all the pleasure of a novelty, as if I had been examining the invention of another.