His good spirits, thanks to his natural vivacity and stamina of constitution, never forsook him; and in his old age, when borne down by disease, he wrote to a friend: "I have gout, asthma, and seven other maladies, but am otherwise very well." In one of the last letters he wrote to Lady Carlisle, he said: "If you hear of sixteen or eighteen pounds of flesh wanting an owner, they belong to me.

I look as if a curate had been taken out of me." Great men of science have for the most part been patient, laborious, cheerful-minded men.

Such were Galileo, Descartes, Newton, and Laplace.
Euler the mathematician, one of the greatest of natural philosophers, was a distinguished instance.

Towards the close of his life he became completely blind; but he went on writing as cheerfully as before, supplying the want of sight by various ingenious mechanical devices, and by the increased cultivation of his memory, which became exceedingly tenacious.

His chief pleasure was in the society of his grandchildren, to whom he taught their little lessons in the intervals of his severer studies.
In like manner, Professor Robison of Edinburgh, the first editor of the 'Encyclopaedia Britannica,' when disabled from work by a lingering and painful disorder, found his chief pleasure in the society of his grandchild.