My provision of the salt, which had never been renewed since the date of the first experiment, began to run low. I sent out for a fresh supply and mixed the draught; the ebullition followed, and the first change of colour, not the second; I drank it and it was without efficiency. You will learn from Poole how I have had London ransacked; it was in vain; and I am now persuaded that my first supply was impure, and that it was that unknown impurity which lent efficacy to the draught.

Chapter 10