Sometimes he remains a whole week without leaving his workroom.

He wears out his eyes over plates and diagrams, bristling with figures and letters, and with no more refreshing thought in the midst of this sore toil than that insult, persecution, torment, trickery, will be the fruit of it.

He not only spent whole days bent over his desk, until he had a feeling as of burning flame within him; he also worked through the hours of the night.
On one of these occasions, worn out with fatigue and weariness, he fell asleep with his head on his desk; the light fell down among his papers, and he awoke to find half the books and papers on the desk burnt to ashes.

"I kept my own counsel about it," he writes, "because a single hint of such an accident would have robbed my wife of sleep for the rest of her life."[200] His favourite form of holiday was a visit to Holbach's country house at Grandval.

Here he spent some six weeks or more nearly every autumn after 1759.